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	$195.98	13.184%	$221.818	$221.82	$221.80	$221.80
Purchase #2	$49.98	12.300%	$56.1275	$56.13	$56.15	$56.10
Purchase #3	$209.50	12.263%	$235.191	$235.19	$235.20	$235.20
Purchase #4	$55.54	11.305%	$61.8188	$61.82	$61.80	$61.80
Purchase #5	$70.88	13.572%	$80.4998	$80.50	$80.50	$80.50
Purchase #6	$10.88	3.461%	$11.2566	$11.26	$11.25	$11.30
Purchase #7	$142.37	5.389%	$150.0423	$150.04	$150.05	$150.00
7 purchase totals =	$735.13		$816.7540	$816.76	$816.75	$816.70