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	$111.41	4.810%	$116.7688	$116.77	$116.75	$116.80
Purchase #2	$81.54	13.590%	$92.6213	$92.62	$92.60	$92.60
Purchase #3	$131.46	10.168%	$144.8269	$144.83	$144.85	$144.80
Purchase #4	$88.56	13.148%	$100.2039	$100.20	$100.20	$100.20
Purchase #5	$59.33	9.388%	$64.8999	$64.90	$64.90	$64.90
Purchase #6	$37.99	9.616%	$41.6431	$41.64	$41.65	$41.60
Purchase #7	$84.61	12.713%	$95.3665	$95.37	$95.35	$95.40
7 purchase totals =	$594.90		$656.3304	$656.33	$656.30	$656.30