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	$64.90	11.188%	$72.161	$72.16	$72.15	$72.20
Purchase #2	$89.56	11.588%	$99.9382	$99.94	$99.95	$99.90
Purchase #3	$148.36	13.483%	$168.3634	$168.36	$168.35	$168.40
Purchase #4	$218.50	4.618%	$228.5903	$228.59	$228.60	$228.60
Purchase #5	$49.53	11.497%	$55.2245	$55.22	$55.20	$55.20
Purchase #6	$135.82	3.185%	$140.1459	$140.15	$140.15	$140.10
Purchase #7	$203.93	11.181%	$226.7314	$226.73	$226.75	$226.70
7 purchase totals =	$910.60		$991.1547	$991.15	$991.15	$991.10