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	$119.30	9.514%	$130.6502	$130.65	$130.65	$130.70
Purchase #2	$134.83	11.611%	$150.4851	$150.49	$150.50	$150.50
Purchase #3	$153.60	13.595%	$174.4819	$174.48	$174.50	$174.50
Purchase #4	$32.27	7.253%	$34.6105	$34.61	$34.60	$34.60
Purchase #5	$66.53	8.675%	$72.3015	$72.30	$72.30	$72.30
Purchase #6	$188.37	13.214%	$213.2612	$213.26	$213.25	$213.30
Purchase #7	$71.87	7.749%	$77.4392	$77.44	$77.45	$77.40
7 purchase totals =	$766.77		$853.2296	$853.23	$853.25	$853.30