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	$43.91	4.401%	$45.8425	$45.84	$45.85	$45.80
Purchase #2	$25.41	3.527%	$26.3062	$26.31	$26.30	$26.30
Purchase #3	$67.98	13.798%	$77.3599	$77.36	$77.35	$77.40
Purchase #4	$141.33	11.234%	$157.207	$157.21	$157.20	$157.20
Purchase #5	$53.47	3.830%	$55.5179	$55.52	$55.50	$55.50
Purchase #6	$128.69	13.335%	$145.8508	$145.85	$145.85	$145.90
Purchase #7	$107.81	3.342%	$111.413	$111.41	$111.40	$111.40
7 purchase totals =	$568.60		$619.4973	$619.50	$619.45	$619.50