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	$226.29	4.790%	$237.1293	$237.13	$237.15	$237.10
Purchase #2	$155.83	9.854%	$171.1855	$171.19	$171.20	$171.20
Purchase #3	$196.55	13.431%	$222.9486	$222.95	$222.95	$222.90
Purchase #4	$64.57	10.411%	$71.2924	$71.29	$71.30	$71.30
Purchase #5	$99.90	6.241%	$106.1348	$106.13	$106.15	$106.10
Purchase #6	$165.77	8.444%	$179.7676	$179.77	$179.75	$179.80
Purchase #7	$155.54	8.474%	$168.7205	$168.72	$168.70	$168.70
7 purchase totals =	$1,064.45		$1,157.1787	$1,157.18	$1,157.20	$1,157.10