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	$40.52	9.409%	$44.3325	$44.33	$44.35	$44.30
Purchase #2	$223.92	9.217%	$244.5587	$244.56	$244.55	$244.60
Purchase #3	$146.48	7.137%	$156.9343	$156.93	$156.95	$156.90
Purchase #4	$204.34	3.846%	$212.1989	$212.20	$212.20	$212.20
Purchase #5	$188.46	4.480%	$196.903	$196.90	$196.90	$196.90
Purchase #6	$160.68	13.785%	$182.8297	$182.83	$182.85	$182.80
Purchase #7	$200.69	10.211%	$221.1825	$221.18	$221.20	$221.20
7 purchase totals =	$1,165.09		$1,258.9396	$1,258.93	$1,259.00	$1,258.90