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	$127.75	4.772%	$133.8462	$133.85	$133.85	$133.80
Purchase #2	$17.56	5.460%	$18.5188	$18.52	$18.50	$18.50
Purchase #3	$40.38	8.118%	$43.658	$43.66	$43.65	$43.70
Purchase #4	$185.36	13.734%	$210.8173	$210.82	$210.80	$210.80
Purchase #5	$79.67	7.334%	$85.513	$85.51	$85.50	$85.50
Purchase #6	$195.46	8.593%	$212.2559	$212.26	$212.25	$212.30
Purchase #7	$109.41	6.637%	$116.6715	$116.67	$116.65	$116.70
7 purchase totals =	$755.59		$821.2807	$821.29	$821.20	$821.30