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	$61.49	4.541%	$64.2823	$64.28	$64.30	$64.30
Purchase #2	$75.25	10.145%	$82.8841	$82.88	$82.90	$82.90
Purchase #3	$45.86	11.838%	$51.2889	$51.29	$51.30	$51.30
Purchase #4	$59.35	7.318%	$63.6932	$63.69	$63.70	$63.70
Purchase #5	$26.93	4.549%	$28.155	$28.16	$28.15	$28.20
Purchase #6	$78.73	13.168%	$89.0972	$89.10	$89.10	$89.10
Purchase #7	$206.28	4.203%	$214.9499	$214.95	$214.95	$214.90
7 purchase totals =	$553.89		$594.3506	$594.35	$594.40	$594.40