Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$161.87	12.670%	$182.3789	$182.38	$182.40	$182.40
Purchase #2	$242.79	9.124%	$264.9422	$264.94	$264.95	$264.90
Purchase #3	$139.54	12.119%	$156.4509	$156.45	$156.45	$156.50
Purchase #4	$205.73	13.631%	$233.7731	$233.77	$233.75	$233.80
Purchase #5	$190.30	3.222%	$196.4315	$196.43	$196.45	$196.40
Purchase #6	$130.26	11.346%	$145.0393	$145.04	$145.05	$145.00
Purchase #7	$236.95	7.573%	$254.8942	$254.89	$254.90	$254.90
7 purchase totals =	$1,307.44		$1,433.9101	$1,433.90	$1,433.95	$1,433.90