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	$119.72	7.596%	$128.8139	$128.81	$128.80	$128.80
Purchase #2	$191.64	6.648%	$204.3802	$204.38	$204.40	$204.40
Purchase #3	$99.65	12.371%	$111.9777	$111.98	$112.00	$112.00
Purchase #4	$31.34	3.267%	$32.3639	$32.36	$32.35	$32.40
Purchase #5	$64.34	3.134%	$66.3564	$66.36	$66.35	$66.40
Purchase #6	$182.76	9.846%	$200.7545	$200.75	$200.75	$200.80
Purchase #7	$26.43	6.502%	$28.1485	$28.15	$28.15	$28.10
7 purchase totals =	$715.88		$772.7951	$772.79	$772.80	$772.90