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	$127.31	8.838%	$138.5617	$138.56	$138.55	$138.60
Purchase #2	$196.51	3.387%	$203.1658	$203.17	$203.15	$203.20
Purchase #3	$11.41	7.618%	$12.2792	$12.28	$12.30	$12.30
Purchase #4	$157.77	10.469%	$174.2869	$174.29	$174.30	$174.30
Purchase #5	$49.55	3.260%	$51.1653	$51.17	$51.15	$51.20
Purchase #6	$82.72	3.215%	$85.3794	$85.38	$85.40	$85.40
Purchase #7	$82.59	13.260%	$93.5414	$93.54	$93.55	$93.50
7 purchase totals =	$707.86		$758.3797	$758.39	$758.40	$758.50