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	$54.72	5.422%	$57.6869	$57.69	$57.70	$57.70
Purchase #2	$59.85	6.772%	$63.903	$63.90	$63.90	$63.90
Purchase #3	$101.58	7.750%	$109.4525	$109.45	$109.45	$109.50
Purchase #4	$81.57	12.500%	$91.7663	$91.77	$91.75	$91.80
Purchase #5	$184.54	9.431%	$201.944	$201.94	$201.95	$201.90
Purchase #6	$159.69	12.674%	$179.9291	$179.93	$179.95	$179.90
Purchase #7	$69.62	13.218%	$78.8224	$78.82	$78.80	$78.80
7 purchase totals =	$711.57		$783.5042	$783.50	$783.50	$783.50