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	$146.83	5.550%	$154.9791	$154.98	$155.00	$155.00
Purchase #2	$190.48	8.598%	$206.8575	$206.86	$206.85	$206.90
Purchase #3	$214.57	3.792%	$222.7065	$222.71	$222.70	$222.70
Purchase #4	$60.67	4.323%	$63.2928	$63.29	$63.30	$63.30
Purchase #5	$215.43	6.330%	$229.0667	$229.07	$229.05	$229.10
Purchase #6	$238.34	3.643%	$247.0227	$247.02	$247.00	$247.00
Purchase #7	$89.28	10.389%	$98.5553	$98.56	$98.55	$98.60
7 purchase totals =	$1,155.60		$1,222.4806	$1,222.49	$1,222.45	$1,222.60