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	$96.36	12.199%	$108.115	$108.12	$108.10	$108.10
Purchase #2	$14.36	4.143%	$14.9549	$14.95	$14.95	$15.00
Purchase #3	$127.72	10.812%	$141.5291	$141.53	$141.55	$141.50
Purchase #4	$193.47	6.237%	$205.5367	$205.54	$205.55	$205.50
Purchase #5	$151.43	11.455%	$168.7763	$168.78	$168.80	$168.80
Purchase #6	$118.53	12.588%	$133.4506	$133.45	$133.45	$133.50
Purchase #7	$192.89	8.379%	$209.0523	$209.05	$209.05	$209.10
7 purchase totals =	$894.76		$981.4149	$981.42	$981.45	$981.50