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	$83.96	8.520%	$91.1134	$91.11	$91.10	$91.10
Purchase #2	$32.68	3.644%	$33.8709	$33.87	$33.85	$33.90
Purchase #3	$221.76	6.718%	$236.6578	$236.66	$236.65	$236.70
Purchase #4	$150.75	4.107%	$156.9413	$156.94	$156.95	$156.90
Purchase #5	$247.52	13.693%	$281.4129	$281.41	$281.40	$281.40
Purchase #6	$50.96	13.333%	$57.7545	$57.75	$57.75	$57.80
Purchase #7	$142.92	6.336%	$151.9754	$151.98	$152.00	$152.00
7 purchase totals =	$930.55		$1,009.7262	$1,009.72	$1,009.70	$1,009.80