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	$163.34	9.761%	$179.2836	$179.28	$179.30	$179.30
Purchase #2	$20.56	5.788%	$21.75	$21.75	$21.75	$21.80
Purchase #3	$158.73	11.404%	$176.8316	$176.83	$176.85	$176.80
Purchase #4	$208.80	9.751%	$229.1601	$229.16	$229.15	$229.20
Purchase #5	$233.65	7.510%	$251.1971	$251.20	$251.20	$251.20
Purchase #6	$46.39	12.555%	$52.2143	$52.21	$52.20	$52.20
Purchase #7	$98.34	13.681%	$111.7939	$111.79	$111.80	$111.80
7 purchase totals =	$929.81		$1,022.2306	$1,022.22	$1,022.25	$1,022.30