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	$165.51	8.827%	$180.1196	$180.12	$180.10	$180.10
Purchase #2	$239.94	9.323%	$262.3096	$262.31	$262.30	$262.30
Purchase #3	$104.71	4.557%	$109.4816	$109.48	$109.50	$109.50
Purchase #4	$151.38	3.223%	$156.259	$156.26	$156.25	$156.30
Purchase #5	$169.63	10.656%	$187.7058	$187.71	$187.70	$187.70
Purchase #6	$7.72	7.191%	$8.2751	$8.28	$8.30	$8.30
Purchase #7	$132.86	13.102%	$150.2673	$150.27	$150.25	$150.30
7 purchase totals =	$971.75		$1,054.4180	$1,054.43	$1,054.40	$1,054.50