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	$213.33	7.275%	$228.8498	$228.85	$228.85	$228.80
Purchase #2	$234.94	9.291%	$256.7683	$256.77	$256.75	$256.80
Purchase #3	$152.42	10.819%	$168.9103	$168.91	$168.90	$168.90
Purchase #4	$77.64	13.472%	$88.0997	$88.10	$88.10	$88.10
Purchase #5	$56.47	6.141%	$59.9378	$59.94	$59.95	$59.90
Purchase #6	$29.70	4.828%	$31.1339	$31.13	$31.15	$31.10
Purchase #7	$67.66	3.557%	$70.0667	$70.07	$70.05	$70.10
7 purchase totals =	$832.16		$903.7665	$903.77	$903.75	$903.70