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	$151.91	3.443%	$157.1403	$157.14	$157.15	$157.10
Purchase #2	$179.93	7.648%	$193.691	$193.69	$193.70	$193.70
Purchase #3	$12.97	12.221%	$14.5551	$14.56	$14.55	$14.60
Purchase #4	$53.65	11.665%	$59.9083	$59.91	$59.90	$59.90
Purchase #5	$105.78	6.648%	$112.8123	$112.81	$112.80	$112.80
Purchase #6	$195.40	11.253%	$217.3884	$217.39	$217.40	$217.40
Purchase #7	$231.66	6.828%	$247.4777	$247.48	$247.50	$247.50
7 purchase totals =	$931.30		$1,002.9731	$1,002.98	$1,003.00	$1,003.00