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	$169.32	8.344%	$183.4481	$183.45	$183.45	$183.40
Purchase #2	$167.92	12.306%	$188.5842	$188.58	$188.60	$188.60
Purchase #3	$78.42	3.818%	$81.4141	$81.41	$81.40	$81.40
Purchase #4	$5.79	4.864%	$6.0716	$6.07	$6.05	$6.10
Purchase #5	$217.57	6.444%	$231.5902	$231.59	$231.60	$231.60
Purchase #6	$174.77	6.416%	$185.9832	$185.98	$186.00	$186.00
Purchase #7	$83.72	6.820%	$89.4297	$89.43	$89.45	$89.40
7 purchase totals =	$897.51		$966.5211	$966.51	$966.55	$966.50