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	$136.74	10.524%	$151.1305	$151.13	$151.15	$151.10
Purchase #2	$12.72	13.700%	$14.4626	$14.46	$14.45	$14.50
Purchase #3	$178.69	9.634%	$195.905	$195.91	$195.90	$195.90
Purchase #4	$112.33	3.110%	$115.8235	$115.82	$115.80	$115.80
Purchase #5	$245.75	8.127%	$265.7221	$265.72	$265.70	$265.70
Purchase #6	$49.56	7.220%	$53.1382	$53.14	$53.15	$53.10
Purchase #7	$70.86	11.389%	$78.9302	$78.93	$78.95	$78.90
7 purchase totals =	$806.65		$875.1121	$875.11	$875.10	$875.00