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	$97.56	8.219%	$105.5785	$105.58	$105.60	$105.60
Purchase #2	$126.52	13.492%	$143.5901	$143.59	$143.60	$143.60
Purchase #3	$30.26	7.783%	$32.6151	$32.62	$32.60	$32.60
Purchase #4	$142.50	5.793%	$150.755	$150.76	$150.75	$150.80
Purchase #5	$199.62	4.823%	$209.2477	$209.25	$209.25	$209.20
Purchase #6	$154.37	10.548%	$170.6529	$170.65	$170.65	$170.70
Purchase #7	$109.90	5.442%	$115.8808	$115.88	$115.90	$115.90
7 purchase totals =	$860.73		$928.3201	$928.33	$928.35	$928.40