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	$67.61	7.644%	$72.7781	$72.78	$72.80	$72.80
Purchase #2	$206.69	5.799%	$218.676	$218.68	$218.70	$218.70
Purchase #3	$76.53	7.826%	$82.5192	$82.52	$82.50	$82.50
Purchase #4	$9.44	6.684%	$10.071	$10.07	$10.05	$10.10
Purchase #5	$124.92	11.740%	$139.5856	$139.59	$139.60	$139.60
Purchase #6	$46.30	9.640%	$50.7633	$50.76	$50.75	$50.80
Purchase #7	$132.94	13.595%	$151.0132	$151.01	$151.00	$151.00
7 purchase totals =	$664.43		$725.4064	$725.41	$725.40	$725.50