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	$62.64	4.496%	$65.4563	$65.46	$65.45	$65.50
Purchase #2	$78.55	8.629%	$85.3281	$85.33	$85.35	$85.30
Purchase #3	$154.92	13.348%	$175.5987	$175.60	$175.60	$175.60
Purchase #4	$221.95	9.539%	$243.1218	$243.12	$243.10	$243.10
Purchase #5	$143.85	6.608%	$153.3556	$153.36	$153.35	$153.40
Purchase #6	$144.55	4.427%	$150.9492	$150.95	$150.95	$150.90
Purchase #7	$200.78	3.871%	$208.5522	$208.55	$208.55	$208.60
7 purchase totals =	$1,007.24		$1,082.3619	$1,082.37	$1,082.35	$1,082.40