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	$136.89	11.700%	$152.9061	$152.91	$152.90	$152.90
Purchase #2	$111.32	8.508%	$120.7911	$120.79	$120.80	$120.80
Purchase #3	$50.72	5.190%	$53.3524	$53.35	$53.35	$53.40
Purchase #4	$157.96	6.332%	$167.962	$167.96	$167.95	$168.00
Purchase #5	$74.75	3.483%	$77.3535	$77.35	$77.35	$77.40
Purchase #6	$199.39	11.428%	$222.1763	$222.18	$222.20	$222.20
Purchase #7	$244.80	7.489%	$263.1331	$263.13	$263.15	$263.10
7 purchase totals =	$975.83		$1,057.6745	$1,057.67	$1,057.70	$1,057.80