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	$141.30	10.336%	$155.9048	$155.90	$155.90	$155.90
Purchase #2	$196.43	13.303%	$222.5611	$222.56	$222.55	$222.60
Purchase #3	$158.58	11.126%	$176.2236	$176.22	$176.20	$176.20
Purchase #4	$139.65	5.357%	$147.1311	$147.13	$147.15	$147.10
Purchase #5	$126.65	12.717%	$142.7561	$142.76	$142.75	$142.80
Purchase #6	$38.88	5.226%	$40.9119	$40.91	$40.90	$40.90
Purchase #7	$216.77	11.760%	$242.2622	$242.26	$242.25	$242.30
7 purchase totals =	$1,018.26		$1,127.7508	$1,127.74	$1,127.70	$1,127.80