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	$148.93	13.528%	$169.0773	$169.08	$169.10	$169.10
Purchase #2	$61.43	12.379%	$69.0344	$69.03	$69.05	$69.00
Purchase #3	$64.69	11.470%	$72.1099	$72.11	$72.10	$72.10
Purchase #4	$55.95	6.405%	$59.5336	$59.53	$59.55	$59.50
Purchase #5	$111.76	10.661%	$123.6747	$123.67	$123.65	$123.70
Purchase #6	$30.35	11.283%	$33.7744	$33.77	$33.75	$33.80
Purchase #7	$190.33	3.448%	$196.8926	$196.89	$196.90	$196.90
7 purchase totals =	$663.44		$724.0969	$724.08	$724.10	$724.10