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	$184.70	4.795%	$193.5564	$193.56	$193.55	$193.60
Purchase #2	$195.63	13.638%	$222.31	$222.31	$222.30	$222.30
Purchase #3	$33.45	7.488%	$35.9547	$35.95	$35.95	$36.00
Purchase #4	$136.33	6.153%	$144.7184	$144.72	$144.70	$144.70
Purchase #5	$63.44	9.577%	$69.5156	$69.52	$69.50	$69.50
Purchase #6	$96.60	9.631%	$105.9035	$105.90	$105.90	$105.90
Purchase #7	$30.58	6.510%	$32.5708	$32.57	$32.55	$32.60
7 purchase totals =	$740.73		$804.5294	$804.53	$804.45	$804.60