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	$250.69	7.646%	$269.8578	$269.86	$269.85	$269.90
Purchase #2	$119.47	7.108%	$127.9619	$127.96	$127.95	$128.00
Purchase #3	$247.56	11.162%	$275.1926	$275.19	$275.20	$275.20
Purchase #4	$102.30	8.869%	$111.373	$111.37	$111.35	$111.40
Purchase #5	$200.31	13.448%	$227.2477	$227.25	$227.25	$227.20
Purchase #6	$49.53	8.210%	$53.5964	$53.60	$53.60	$53.60
Purchase #7	$240.89	6.652%	$256.914	$256.91	$256.90	$256.90
7 purchase totals =	$1,210.75		$1,322.1434	$1,322.14	$1,322.10	$1,322.20