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	$123.51	7.332%	$132.5658	$132.57	$132.55	$132.60
Purchase #2	$28.26	4.344%	$29.4876	$29.49	$29.50	$29.50
Purchase #3	$169.88	5.270%	$178.8327	$178.83	$178.85	$178.80
Purchase #4	$246.43	4.749%	$258.133	$258.13	$258.15	$258.10
Purchase #5	$80.81	13.226%	$91.4979	$91.50	$91.50	$91.50
Purchase #6	$242.85	13.394%	$275.3773	$275.38	$275.40	$275.40
Purchase #7	$35.95	7.140%	$38.5168	$38.52	$38.50	$38.50
7 purchase totals =	$927.69		$1,004.4111	$1,004.42	$1,004.45	$1,004.40