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	$214.78	13.306%	$243.3586	$243.36	$243.35	$243.40
Purchase #2	$163.33	4.740%	$171.0718	$171.07	$171.05	$171.10
Purchase #3	$40.30	12.527%	$45.3484	$45.35	$45.35	$45.30
Purchase #4	$11.33	12.621%	$12.76	$12.76	$12.75	$12.80
Purchase #5	$224.90	13.774%	$255.8777	$255.88	$255.90	$255.90
Purchase #6	$173.93	12.478%	$195.633	$195.63	$195.65	$195.60
Purchase #7	$67.55	5.497%	$71.2632	$71.26	$71.25	$71.30
7 purchase totals =	$896.12		$995.3127	$995.31	$995.30	$995.40