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	$147.41	3.672%	$152.8229	$152.82	$152.80	$152.80
Purchase #2	$244.33	13.753%	$277.9327	$277.93	$277.95	$277.90
Purchase #3	$210.75	13.437%	$239.0685	$239.07	$239.05	$239.10
Purchase #4	$233.70	12.360%	$262.5853	$262.59	$262.60	$262.60
Purchase #5	$105.92	5.676%	$111.932	$111.93	$111.95	$111.90
Purchase #6	$63.40	10.664%	$70.161	$70.16	$70.15	$70.20
Purchase #7	$195.83	6.418%	$208.3984	$208.40	$208.40	$208.40
7 purchase totals =	$1,201.34		$1,322.9008	$1,322.90	$1,322.90	$1,322.90