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	$172.84	4.549%	$180.7025	$180.70	$180.70	$180.70
Purchase #2	$201.55	9.731%	$221.1628	$221.16	$221.15	$221.20
Purchase #3	$125.40	5.180%	$131.8957	$131.90	$131.90	$131.90
Purchase #4	$84.51	5.433%	$89.1014	$89.10	$89.10	$89.10
Purchase #5	$214.28	11.129%	$238.1272	$238.13	$238.15	$238.10
Purchase #6	$179.87	13.650%	$204.4223	$204.42	$204.40	$204.40
Purchase #7	$97.27	9.561%	$106.57	$106.57	$106.55	$106.60
7 purchase totals =	$1,075.72		$1,171.9819	$1,171.98	$1,171.95	$1,172.00