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	$70.75	10.162%	$77.9396	$77.94	$77.95	$77.90
Purchase #2	$163.52	7.111%	$175.1479	$175.15	$175.15	$175.10
Purchase #3	$94.78	6.122%	$100.5824	$100.58	$100.60	$100.60
Purchase #4	$187.60	6.151%	$199.1393	$199.14	$199.15	$199.10
Purchase #5	$22.78	5.673%	$24.0723	$24.07	$24.05	$24.10
Purchase #6	$86.51	10.281%	$95.4041	$95.40	$95.40	$95.40
Purchase #7	$74.61	5.644%	$78.821	$78.82	$78.80	$78.80
7 purchase totals =	$700.55		$751.1066	$751.10	$751.10	$751.00