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	$63.75	6.605%	$67.9607	$67.96	$67.95	$68.00
Purchase #2	$68.96	13.327%	$78.1503	$78.15	$78.15	$78.20
Purchase #3	$214.57	13.778%	$244.1335	$244.13	$244.15	$244.10
Purchase #4	$131.97	6.818%	$140.9677	$140.97	$140.95	$141.00
Purchase #5	$116.54	12.689%	$131.3278	$131.33	$131.35	$131.30
Purchase #6	$239.54	12.422%	$269.2957	$269.30	$269.30	$269.30
Purchase #7	$114.41	13.323%	$129.6528	$129.65	$129.65	$129.70
7 purchase totals =	$949.74		$1,061.4885	$1,061.49	$1,061.50	$1,061.60