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	$138.71	5.194%	$145.9146	$145.91	$145.90	$145.90
Purchase #2	$187.27	13.352%	$212.2743	$212.27	$212.25	$212.30
Purchase #3	$195.49	13.321%	$221.5312	$221.53	$221.55	$221.50
Purchase #4	$215.57	3.344%	$222.7787	$222.78	$222.80	$222.80
Purchase #5	$188.27	11.873%	$210.6233	$210.62	$210.60	$210.60
Purchase #6	$240.66	7.843%	$259.535	$259.54	$259.55	$259.50
Purchase #7	$118.60	8.536%	$128.7237	$128.72	$128.70	$128.70
7 purchase totals =	$1,284.57		$1,401.3808	$1,401.37	$1,401.35	$1,401.30