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	$130.89	4.861%	$137.2526	$137.25	$137.25	$137.30
Purchase #2	$181.70	5.570%	$191.8207	$191.82	$191.80	$191.80
Purchase #3	$125.32	13.271%	$141.9512	$141.95	$141.95	$142.00
Purchase #4	$202.46	13.131%	$229.045	$229.05	$229.05	$229.00
Purchase #5	$206.86	9.207%	$225.9056	$225.91	$225.90	$225.90
Purchase #6	$230.59	7.772%	$248.5115	$248.51	$248.50	$248.50
Purchase #7	$83.95	8.575%	$91.1487	$91.15	$91.15	$91.10
7 purchase totals =	$1,161.77		$1,265.6353	$1,265.64	$1,265.60	$1,265.60