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	$196.91	7.545%	$211.7669	$211.77	$211.75	$211.80
Purchase #2	$125.83	3.390%	$130.0956	$130.10	$130.10	$130.10
Purchase #3	$131.65	5.527%	$138.9263	$138.93	$138.95	$138.90
Purchase #4	$76.61	7.282%	$82.1887	$82.19	$82.20	$82.20
Purchase #5	$219.44	5.516%	$231.5443	$231.54	$231.55	$231.50
Purchase #6	$51.29	5.769%	$54.2489	$54.25	$54.25	$54.20
Purchase #7	$54.88	12.672%	$61.8344	$61.83	$61.85	$61.80
7 purchase totals =	$856.61		$910.6051	$910.61	$910.65	$910.50