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	$145.61	4.714%	$152.4741	$152.47	$152.45	$152.50
Purchase #2	$248.62	10.846%	$275.5853	$275.59	$275.60	$275.60
Purchase #3	$99.59	5.460%	$105.0276	$105.03	$105.05	$105.00
Purchase #4	$28.47	6.624%	$30.3559	$30.36	$30.35	$30.40
Purchase #5	$78.46	13.837%	$89.3165	$89.32	$89.30	$89.30
Purchase #6	$67.66	11.854%	$75.6804	$75.68	$75.70	$75.70
Purchase #7	$121.47	3.330%	$125.515	$125.52	$125.50	$125.50
7 purchase totals =	$789.88		$853.9548	$853.97	$853.95	$854.00