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	$218.31	9.421%	$238.877	$238.88	$238.90	$238.90
Purchase #2	$202.77	5.841%	$214.6138	$214.61	$214.60	$214.60
Purchase #3	$182.59	9.296%	$199.5636	$199.56	$199.55	$199.60
Purchase #4	$180.37	10.606%	$199.5	$199.50	$199.50	$199.50
Purchase #5	$165.77	4.864%	$173.8331	$173.83	$173.85	$173.80
Purchase #6	$30.47	7.717%	$32.8214	$32.82	$32.80	$32.80
Purchase #7	$179.61	9.819%	$197.2459	$197.25	$197.25	$197.20
7 purchase totals =	$1,159.89		$1,256.4548	$1,256.45	$1,256.45	$1,256.40