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	$219.27	10.238%	$241.7189	$241.72	$241.70	$241.70
Purchase #2	$71.88	9.747%	$78.8861	$78.89	$78.90	$78.90
Purchase #3	$37.63	8.186%	$40.7104	$40.71	$40.70	$40.70
Purchase #4	$230.85	11.689%	$257.8341	$257.83	$257.85	$257.80
Purchase #5	$27.94	6.721%	$29.8178	$29.82	$29.80	$29.80
Purchase #6	$221.92	10.530%	$245.2882	$245.29	$245.30	$245.30
Purchase #7	$6.80	12.740%	$7.6663	$7.67	$7.65	$7.70
7 purchase totals =	$816.29		$901.9218	$901.93	$901.90	$901.90