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	$149.32	13.784%	$169.9023	$169.90	$169.90	$169.90
Purchase #2	$99.32	12.206%	$111.443	$111.44	$111.45	$111.40
Purchase #3	$48.95	3.439%	$50.6334	$50.63	$50.65	$50.60
Purchase #4	$89.83	7.501%	$96.5681	$96.57	$96.55	$96.60
Purchase #5	$33.65	11.166%	$37.4074	$37.41	$37.40	$37.40
Purchase #6	$11.88	11.347%	$13.228	$13.23	$13.25	$13.20
Purchase #7	$79.30	7.794%	$85.4806	$85.48	$85.50	$85.50
7 purchase totals =	$512.25		$564.6628	$564.66	$564.70	$564.60