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	$242.95	5.755%	$256.9318	$256.93	$256.95	$256.90
Purchase #2	$47.88	4.763%	$50.1605	$50.16	$50.15	$50.20
Purchase #3	$30.86	7.816%	$33.272	$33.27	$33.25	$33.30
Purchase #4	$161.26	8.465%	$174.9107	$174.91	$174.90	$174.90
Purchase #5	$220.34	5.790%	$233.0977	$233.10	$233.10	$233.10
Purchase #6	$214.94	6.862%	$229.6892	$229.69	$229.70	$229.70
Purchase #7	$67.71	6.730%	$72.2669	$72.27	$72.25	$72.30
7 purchase totals =	$985.94		$1,050.3288	$1,050.33	$1,050.30	$1,050.40