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	$182.29	3.284%	$188.2764	$188.28	$188.30	$188.30
Purchase #2	$63.33	13.638%	$71.9669	$71.97	$71.95	$72.00
Purchase #3	$244.88	10.640%	$270.9352	$270.94	$270.95	$270.90
Purchase #4	$202.96	12.812%	$228.9632	$228.96	$228.95	$229.00
Purchase #5	$122.89	13.188%	$139.0967	$139.10	$139.10	$139.10
Purchase #6	$35.81	13.481%	$40.6375	$40.64	$40.65	$40.60
Purchase #7	$114.71	6.179%	$121.7979	$121.80	$121.80	$121.80
7 purchase totals =	$966.87		$1,061.6738	$1,061.69	$1,061.70	$1,061.70