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	$219.53	3.773%	$227.8129	$227.81	$227.80	$227.80
Purchase #2	$227.28	12.460%	$255.5991	$255.60	$255.60	$255.60
Purchase #3	$143.73	6.389%	$152.9129	$152.91	$152.90	$152.90
Purchase #4	$6.49	12.444%	$7.2976	$7.30	$7.30	$7.30
Purchase #5	$110.48	7.695%	$118.9814	$118.98	$119.00	$119.00
Purchase #6	$67.28	6.330%	$71.5388	$71.54	$71.55	$71.50
Purchase #7	$238.66	10.653%	$264.0844	$264.08	$264.10	$264.10
7 purchase totals =	$1,013.45		$1,098.2271	$1,098.22	$1,098.25	$1,098.20