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	$212.96	10.242%	$234.7714	$234.77	$234.75	$234.80
Purchase #2	$75.96	11.797%	$84.921	$84.92	$84.90	$84.90
Purchase #3	$37.76	12.840%	$42.6084	$42.61	$42.60	$42.60
Purchase #4	$176.67	13.298%	$200.1636	$200.16	$200.15	$200.20
Purchase #5	$35.95	6.390%	$38.2472	$38.25	$38.25	$38.20
Purchase #6	$119.82	13.104%	$135.5212	$135.52	$135.50	$135.50
Purchase #7	$80.74	10.408%	$89.1434	$89.14	$89.15	$89.10
7 purchase totals =	$739.86		$825.3762	$825.37	$825.30	$825.30