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	$72.92	7.447%	$78.3504	$78.35	$78.35	$78.40
Purchase #2	$138.49	5.461%	$146.0529	$146.05	$146.05	$146.10
Purchase #3	$30.62	3.217%	$31.605	$31.61	$31.60	$31.60
Purchase #4	$199.94	5.764%	$211.4645	$211.46	$211.45	$211.50
Purchase #5	$33.73	11.645%	$37.6579	$37.66	$37.65	$37.70
Purchase #6	$198.37	13.238%	$224.6302	$224.63	$224.65	$224.60
Purchase #7	$98.45	7.135%	$105.4744	$105.47	$105.45	$105.50
7 purchase totals =	$772.52		$835.2353	$835.23	$835.20	$835.40