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	$182.96	5.606%	$193.2167	$193.22	$193.20	$193.20
Purchase #2	$227.39	10.307%	$250.8271	$250.83	$250.85	$250.80
Purchase #3	$202.48	11.550%	$225.8664	$225.87	$225.85	$225.90
Purchase #4	$54.27	10.126%	$59.7654	$59.77	$59.75	$59.80
Purchase #5	$227.88	12.761%	$256.9598	$256.96	$256.95	$257.00
Purchase #6	$88.93	11.270%	$98.9524	$98.95	$98.95	$99.00
Purchase #7	$100.31	11.164%	$111.5086	$111.51	$111.50	$111.50
7 purchase totals =	$1,084.22		$1,197.0964	$1,197.11	$1,197.05	$1,197.20