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	$184.96	3.652%	$191.7147	$191.71	$191.70	$191.70
Purchase #2	$19.67	11.213%	$21.8756	$21.88	$21.90	$21.90
Purchase #3	$210.98	9.785%	$231.6244	$231.62	$231.60	$231.60
Purchase #4	$218.82	13.244%	$247.8005	$247.80	$247.80	$247.80
Purchase #5	$199.39	12.133%	$223.582	$223.58	$223.60	$223.60
Purchase #6	$231.94	3.108%	$239.1487	$239.15	$239.15	$239.10
Purchase #7	$61.50	9.333%	$67.2398	$67.24	$67.25	$67.20
7 purchase totals =	$1,127.26		$1,222.9857	$1,222.98	$1,223.00	$1,222.90