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	$59.79	7.826%	$64.4692	$64.47	$64.45	$64.50
Purchase #2	$174.54	6.240%	$185.4313	$185.43	$185.45	$185.40
Purchase #3	$164.50	12.514%	$185.0855	$185.09	$185.10	$185.10
Purchase #4	$155.68	12.502%	$175.1431	$175.14	$175.15	$175.10
Purchase #5	$131.95	13.207%	$149.3766	$149.38	$149.40	$149.40
Purchase #6	$219.78	6.298%	$233.6217	$233.62	$233.60	$233.60
Purchase #7	$50.97	8.297%	$55.199	$55.20	$55.20	$55.20
7 purchase totals =	$957.21		$1,048.3264	$1,048.33	$1,048.35	$1,048.30