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	$41.41	12.849%	$46.7308	$46.73	$46.75	$46.70
Purchase #2	$205.47	8.291%	$222.5055	$222.51	$222.50	$222.50
Purchase #3	$147.62	11.734%	$164.9417	$164.94	$164.95	$164.90
Purchase #4	$166.49	11.439%	$185.5348	$185.53	$185.55	$185.50
Purchase #5	$169.72	5.642%	$179.2956	$179.30	$179.30	$179.30
Purchase #6	$196.28	8.116%	$212.2101	$212.21	$212.20	$212.20
Purchase #7	$163.85	9.480%	$179.383	$179.38	$179.40	$179.40
7 purchase totals =	$1,090.84		$1,190.6015	$1,190.60	$1,190.65	$1,190.50