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	$31.65	10.355%	$34.9274	$34.93	$34.95	$34.90
Purchase #2	$145.53	6.872%	$155.5308	$155.53	$155.55	$155.50
Purchase #3	$219.83	10.360%	$242.6044	$242.60	$242.60	$242.60
Purchase #4	$76.48	7.613%	$82.3024	$82.30	$82.30	$82.30
Purchase #5	$215.87	5.394%	$227.514	$227.51	$227.50	$227.50
Purchase #6	$39.82	6.354%	$42.3502	$42.35	$42.35	$42.40
Purchase #7	$189.92	10.515%	$209.8901	$209.89	$209.90	$209.90
7 purchase totals =	$919.10		$995.1193	$995.11	$995.15	$995.10