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	$162.94	11.848%	$182.2451	$182.25	$182.25	$182.20
Purchase #2	$52.53	12.378%	$59.0322	$59.03	$59.05	$59.00
Purchase #3	$45.87	7.335%	$49.2346	$49.23	$49.25	$49.20
Purchase #4	$37.37	8.830%	$40.6698	$40.67	$40.65	$40.70
Purchase #5	$245.34	12.346%	$275.6297	$275.63	$275.65	$275.60
Purchase #6	$175.71	13.130%	$198.7807	$198.78	$198.80	$198.80
Purchase #7	$56.53	13.753%	$64.3046	$64.30	$64.30	$64.30
7 purchase totals =	$776.29		$869.8967	$869.89	$869.95	$869.80