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	$117.57	13.401%	$133.3256	$133.33	$133.35	$133.30
Purchase #2	$107.72	7.723%	$116.0392	$116.04	$116.05	$116.00
Purchase #3	$189.95	8.398%	$205.902	$205.90	$205.90	$205.90
Purchase #4	$210.52	13.233%	$238.3781	$238.38	$238.40	$238.40
Purchase #5	$248.54	6.547%	$264.8119	$264.81	$264.80	$264.80
Purchase #6	$52.76	11.234%	$58.6871	$58.69	$58.70	$58.70
Purchase #7	$104.54	6.420%	$111.2515	$111.25	$111.25	$111.30
7 purchase totals =	$1,031.60		$1,128.3954	$1,128.40	$1,128.45	$1,128.40