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	$127.64	3.171%	$131.6875	$131.69	$131.70	$131.70
Purchase #2	$68.62	4.215%	$71.5123	$71.51	$71.50	$71.50
Purchase #3	$206.36	10.733%	$228.5086	$228.51	$228.50	$228.50
Purchase #4	$145.80	10.489%	$161.093	$161.09	$161.10	$161.10
Purchase #5	$188.54	13.122%	$213.2802	$213.28	$213.30	$213.30
Purchase #6	$168.73	7.373%	$181.1705	$181.17	$181.15	$181.20
Purchase #7	$109.95	13.299%	$124.5723	$124.57	$124.55	$124.60
7 purchase totals =	$1,015.64		$1,111.8244	$1,111.82	$1,111.80	$1,111.90