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	$118.26	10.641%	$130.844	$130.84	$130.85	$130.80
Purchase #2	$33.42	11.692%	$37.3275	$37.33	$37.35	$37.30
Purchase #3	$224.31	4.217%	$233.7692	$233.77	$233.75	$233.80
Purchase #4	$77.42	4.456%	$80.8698	$80.87	$80.85	$80.90
Purchase #5	$173.81	8.662%	$188.8654	$188.87	$188.85	$188.90
Purchase #6	$208.34	3.355%	$215.3298	$215.33	$215.35	$215.30
Purchase #7	$74.29	5.174%	$78.1338	$78.13	$78.15	$78.10
7 purchase totals =	$909.85		$965.1395	$965.14	$965.15	$965.10