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	$141.77	11.808%	$158.5102	$158.51	$158.50	$158.50
Purchase #2	$155.54	5.797%	$164.5567	$164.56	$164.55	$164.60
Purchase #3	$145.58	9.532%	$159.4567	$159.46	$159.45	$159.50
Purchase #4	$57.83	4.805%	$60.6087	$60.61	$60.60	$60.60
Purchase #5	$208.73	9.857%	$229.3045	$229.30	$229.30	$229.30
Purchase #6	$45.68	4.564%	$47.7648	$47.76	$47.75	$47.80
Purchase #7	$82.70	4.731%	$86.6125	$86.61	$86.60	$86.60
7 purchase totals =	$837.83		$906.8141	$906.81	$906.75	$906.90