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	$114.64	8.746%	$124.6664	$124.67	$124.65	$124.70
Purchase #2	$85.46	6.869%	$91.3302	$91.33	$91.35	$91.30
Purchase #3	$52.93	11.227%	$58.8725	$58.87	$58.85	$58.90
Purchase #4	$37.32	5.701%	$39.4476	$39.45	$39.45	$39.40
Purchase #5	$76.32	8.123%	$82.5195	$82.52	$82.50	$82.50
Purchase #6	$47.75	7.659%	$51.4072	$51.41	$51.40	$51.40
Purchase #7	$148.62	5.870%	$157.344	$157.34	$157.35	$157.30
7 purchase totals =	$563.04		$605.5874	$605.59	$605.55	$605.50