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	$224.54	5.653%	$237.2332	$237.23	$237.25	$237.20
Purchase #2	$147.33	3.268%	$152.1447	$152.14	$152.15	$152.10
Purchase #3	$88.28	13.447%	$100.151	$100.15	$100.15	$100.20
Purchase #4	$33.89	11.571%	$37.8114	$37.81	$37.80	$37.80
Purchase #5	$49.36	9.490%	$54.0443	$54.04	$54.05	$54.00
Purchase #6	$239.69	5.781%	$253.5465	$253.55	$253.55	$253.50
Purchase #7	$131.82	13.251%	$149.2875	$149.29	$149.30	$149.30
7 purchase totals =	$914.91		$984.2186	$984.21	$984.25	$984.10