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	$157.62	9.616%	$172.7767	$172.78	$172.80	$172.80
Purchase #2	$134.29	8.417%	$145.5932	$145.59	$145.60	$145.60
Purchase #3	$243.76	4.621%	$255.0241	$255.02	$255.00	$255.00
Purchase #4	$214.65	3.533%	$222.2336	$222.23	$222.25	$222.20
Purchase #5	$240.54	4.329%	$250.953	$250.95	$250.95	$251.00
Purchase #6	$179.31	9.847%	$196.9667	$196.97	$196.95	$197.00
Purchase #7	$116.26	10.583%	$128.5638	$128.56	$128.55	$128.60
7 purchase totals =	$1,286.43		$1,372.1111	$1,372.10	$1,372.10	$1,372.20