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	$174.53	3.452%	$180.5548	$180.55	$180.55	$180.60
Purchase #2	$170.37	4.233%	$177.5818	$177.58	$177.60	$177.60
Purchase #3	$28.52	13.155%	$32.2718	$32.27	$32.25	$32.30
Purchase #4	$225.91	4.375%	$235.7936	$235.79	$235.80	$235.80
Purchase #5	$127.46	10.498%	$140.8408	$140.84	$140.85	$140.80
Purchase #6	$236.35	8.573%	$256.6123	$256.61	$256.60	$256.60
Purchase #7	$156.41	10.649%	$173.0661	$173.07	$173.05	$173.10
7 purchase totals =	$1,119.55		$1,196.7212	$1,196.71	$1,196.70	$1,196.80