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	$36.29	5.584%	$38.3164	$38.32	$38.30	$38.30
Purchase #2	$85.39	6.707%	$91.1171	$91.12	$91.10	$91.10
Purchase #3	$152.94	13.151%	$173.0531	$173.05	$173.05	$173.10
Purchase #4	$98.48	13.679%	$111.9511	$111.95	$111.95	$112.00
Purchase #5	$232.81	7.627%	$250.5664	$250.57	$250.55	$250.60
Purchase #6	$32.47	10.855%	$35.9946	$35.99	$36.00	$36.00
Purchase #7	$11.36	10.254%	$12.5249	$12.52	$12.50	$12.50
7 purchase totals =	$649.74		$713.5236	$713.52	$713.45	$713.60