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	$225.52	7.268%	$241.9108	$241.91	$241.90	$241.90
Purchase #2	$28.88	10.305%	$31.8561	$31.86	$31.85	$31.90
Purchase #3	$50.67	3.434%	$52.41	$52.41	$52.40	$52.40
Purchase #4	$50.55	10.159%	$55.6854	$55.69	$55.70	$55.70
Purchase #5	$29.61	10.264%	$32.6492	$32.65	$32.65	$32.60
Purchase #6	$153.93	13.848%	$175.2462	$175.25	$175.25	$175.20
Purchase #7	$17.98	10.648%	$19.8945	$19.89	$19.90	$19.90
7 purchase totals =	$557.14		$609.6522	$609.66	$609.65	$609.60