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	$169.43	9.303%	$185.1921	$185.19	$185.20	$185.20
Purchase #2	$114.31	7.650%	$123.0547	$123.05	$123.05	$123.10
Purchase #3	$78.76	6.588%	$83.9487	$83.95	$83.95	$83.90
Purchase #4	$176.67	4.828%	$185.1996	$185.20	$185.20	$185.20
Purchase #5	$30.87	9.789%	$33.8919	$33.89	$33.90	$33.90
Purchase #6	$147.88	12.345%	$166.1358	$166.14	$166.15	$166.10
Purchase #7	$20.82	8.512%	$22.5922	$22.59	$22.60	$22.60
7 purchase totals =	$738.74		$800.0150	$800.01	$800.05	$800.00