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	$204.56	11.727%	$228.5488	$228.55	$228.55	$228.50
Purchase #2	$101.67	11.219%	$113.0764	$113.08	$113.10	$113.10
Purchase #3	$148.34	12.226%	$166.476	$166.48	$166.50	$166.50
Purchase #4	$28.73	12.482%	$32.3161	$32.32	$32.30	$32.30
Purchase #5	$100.26	10.487%	$110.7743	$110.77	$110.75	$110.80
Purchase #6	$246.73	11.377%	$274.8005	$274.80	$274.80	$274.80
Purchase #7	$211.29	5.243%	$222.3679	$222.37	$222.35	$222.40
7 purchase totals =	$1,041.58		$1,148.3600	$1,148.37	$1,148.35	$1,148.40