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	$110.64	11.381%	$123.2319	$123.23	$123.25	$123.20
Purchase #2	$99.42	11.868%	$111.2192	$111.22	$111.20	$111.20
Purchase #3	$153.77	3.674%	$159.4195	$159.42	$159.40	$159.40
Purchase #4	$225.28	10.742%	$249.4796	$249.48	$249.50	$249.50
Purchase #5	$197.77	6.447%	$210.5202	$210.52	$210.50	$210.50
Purchase #6	$16.33	10.361%	$18.022	$18.02	$18.00	$18.00
Purchase #7	$159.42	11.596%	$177.9063	$177.91	$177.90	$177.90
7 purchase totals =	$962.63		$1,049.7987	$1,049.80	$1,049.75	$1,049.70