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	$93.65	13.468%	$106.2628	$106.26	$106.25	$106.30
Purchase #2	$234.59	8.851%	$255.3536	$255.35	$255.35	$255.40
Purchase #3	$128.78	4.297%	$134.3137	$134.31	$134.30	$134.30
Purchase #4	$38.90	11.411%	$43.3389	$43.34	$43.35	$43.30
Purchase #5	$139.90	10.128%	$154.0691	$154.07	$154.05	$154.10
Purchase #6	$244.76	11.331%	$272.4938	$272.49	$272.50	$272.50
Purchase #7	$64.77	3.681%	$67.1542	$67.15	$67.15	$67.20
7 purchase totals =	$945.35		$1,032.9861	$1,032.97	$1,032.95	$1,033.10