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	$71.91	5.174%	$75.6306	$75.63	$75.65	$75.60
Purchase #2	$67.39	13.619%	$76.5678	$76.57	$76.55	$76.60
Purchase #3	$20.44	8.204%	$22.1169	$22.12	$22.10	$22.10
Purchase #4	$9.56	8.466%	$10.3693	$10.37	$10.35	$10.40
Purchase #5	$76.43	8.439%	$82.8799	$82.88	$82.90	$82.90
Purchase #6	$16.66	13.304%	$18.8764	$18.88	$18.90	$18.90
Purchase #7	$98.45	13.682%	$111.9199	$111.92	$111.90	$111.90
7 purchase totals =	$360.84		$398.3608	$398.37	$398.35	$398.40