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	$77.48	10.770%	$85.8246	$85.82	$85.80	$85.80
Purchase #2	$81.34	11.260%	$90.4989	$90.50	$90.50	$90.50
Purchase #3	$128.97	9.801%	$141.6103	$141.61	$141.60	$141.60
Purchase #4	$8.33	3.574%	$8.6277	$8.63	$8.65	$8.60
Purchase #5	$95.58	11.654%	$106.7189	$106.72	$106.70	$106.70
Purchase #6	$116.60	10.118%	$128.3976	$128.40	$128.40	$128.40
Purchase #7	$177.70	3.839%	$184.5219	$184.52	$184.50	$184.50
7 purchase totals =	$686.00		$746.1999	$746.20	$746.15	$746.10