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	$221.29	6.534%	$235.7491	$235.75	$235.75	$235.70
Purchase #2	$78.82	4.673%	$82.5033	$82.50	$82.50	$82.50
Purchase #3	$17.48	10.338%	$19.2871	$19.29	$19.30	$19.30
Purchase #4	$99.41	6.548%	$105.9194	$105.92	$105.90	$105.90
Purchase #5	$130.29	10.411%	$143.8545	$143.85	$143.85	$143.90
Purchase #6	$129.46	6.331%	$137.6561	$137.66	$137.65	$137.70
Purchase #7	$151.41	3.145%	$156.1718	$156.17	$156.15	$156.20
7 purchase totals =	$828.16		$881.1413	$881.14	$881.10	$881.20