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	$47.72	12.704%	$53.7823	$53.78	$53.80	$53.80
Purchase #2	$203.46	6.340%	$216.3594	$216.36	$216.35	$216.40
Purchase #3	$32.71	6.454%	$34.8211	$34.82	$34.80	$34.80
Purchase #4	$236.65	8.409%	$256.5499	$256.55	$256.55	$256.50
Purchase #5	$31.98	3.297%	$33.0344	$33.03	$33.05	$33.00
Purchase #6	$69.32	5.110%	$72.8623	$72.86	$72.85	$72.90
Purchase #7	$118.55	10.637%	$131.1602	$131.16	$131.15	$131.20
7 purchase totals =	$740.39		$798.5696	$798.56	$798.55	$798.60