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	$42.80	12.642%	$48.2108	$48.21	$48.20	$48.20
Purchase #2	$166.31	3.525%	$172.1724	$172.17	$172.15	$172.20
Purchase #3	$37.29	3.853%	$38.7268	$38.73	$38.75	$38.70
Purchase #4	$117.92	11.376%	$131.3346	$131.33	$131.35	$131.30
Purchase #5	$55.25	10.114%	$60.838	$60.84	$60.85	$60.80
Purchase #6	$157.88	8.470%	$171.2524	$171.25	$171.25	$171.30
Purchase #7	$63.69	13.498%	$72.2869	$72.29	$72.30	$72.30
7 purchase totals =	$641.14		$694.8219	$694.82	$694.85	$694.80