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	$180.53	8.582%	$196.0231	$196.02	$196.00	$196.00
Purchase #2	$20.36	7.530%	$21.8931	$21.89	$21.90	$21.90
Purchase #3	$208.30	7.363%	$223.6371	$223.64	$223.65	$223.60
Purchase #4	$101.97	3.604%	$105.645	$105.65	$105.65	$105.60
Purchase #5	$63.89	11.496%	$71.2348	$71.23	$71.25	$71.20
Purchase #6	$168.41	13.499%	$191.1437	$191.14	$191.15	$191.10
Purchase #7	$170.68	8.810%	$185.7169	$185.72	$185.70	$185.70
7 purchase totals =	$914.14		$995.2937	$995.29	$995.30	$995.10