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	$35.45	4.118%	$36.9098	$36.91	$36.90	$36.90
Purchase #2	$218.58	11.688%	$244.1276	$244.13	$244.15	$244.10
Purchase #3	$52.44	3.406%	$54.2261	$54.23	$54.25	$54.20
Purchase #4	$31.72	4.559%	$33.1661	$33.17	$33.15	$33.20
Purchase #5	$210.80	3.852%	$218.92	$218.92	$218.90	$218.90
Purchase #6	$21.52	4.123%	$22.4073	$22.41	$22.40	$22.40
Purchase #7	$39.49	7.318%	$42.3799	$42.38	$42.40	$42.40
7 purchase totals =	$610.00		$652.1368	$652.15	$652.15	$652.10