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	$205.72	12.855%	$232.1653	$232.17	$232.15	$232.20
Purchase #2	$41.34	12.147%	$46.3616	$46.36	$46.35	$46.40
Purchase #3	$20.76	3.867%	$21.5628	$21.56	$21.55	$21.60
Purchase #4	$189.87	5.406%	$200.1344	$200.13	$200.15	$200.10
Purchase #5	$184.59	13.874%	$210.2	$210.20	$210.20	$210.20
Purchase #6	$112.53	3.443%	$116.4044	$116.40	$116.40	$116.40
Purchase #7	$61.64	9.231%	$67.33	$67.33	$67.35	$67.30
7 purchase totals =	$816.45		$894.1585	$894.15	$894.15	$894.20