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	$220.95	12.163%	$247.8241	$247.82	$247.80	$247.80
Purchase #2	$64.32	9.680%	$70.5462	$70.55	$70.55	$70.50
Purchase #3	$139.95	5.835%	$148.1161	$148.12	$148.10	$148.10
Purchase #4	$142.99	9.188%	$156.1279	$156.13	$156.15	$156.10
Purchase #5	$234.32	9.191%	$255.8564	$255.86	$255.85	$255.90
Purchase #6	$11.97	6.373%	$12.7328	$12.73	$12.75	$12.70
Purchase #7	$119.74	9.822%	$131.5009	$131.50	$131.50	$131.50
7 purchase totals =	$934.24		$1,022.7044	$1,022.71	$1,022.70	$1,022.60