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	$128.34	4.624%	$134.2744	$134.27	$134.25	$134.30
Purchase #2	$99.67	11.332%	$110.9646	$110.96	$110.95	$111.00
Purchase #3	$227.69	12.127%	$255.302	$255.30	$255.30	$255.30
Purchase #4	$25.29	10.297%	$27.8941	$27.89	$27.90	$27.90
Purchase #5	$142.38	11.409%	$158.6241	$158.62	$158.60	$158.60
Purchase #6	$186.72	4.103%	$194.3811	$194.38	$194.40	$194.40
Purchase #7	$47.87	10.167%	$52.7369	$52.74	$52.75	$52.70
7 purchase totals =	$857.96		$934.1772	$934.16	$934.15	$934.20