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	$113.74	4.381%	$118.7229	$118.72	$118.70	$118.70
Purchase #2	$44.91	10.144%	$49.4657	$49.47	$49.45	$49.50
Purchase #3	$151.84	12.220%	$170.3948	$170.39	$170.40	$170.40
Purchase #4	$39.34	4.852%	$41.2488	$41.25	$41.25	$41.20
Purchase #5	$62.83	13.692%	$71.4327	$71.43	$71.45	$71.40
Purchase #6	$127.52	9.643%	$139.8168	$139.82	$139.80	$139.80
Purchase #7	$77.67	9.741%	$85.2358	$85.24	$85.25	$85.20
7 purchase totals =	$617.85		$676.3175	$676.32	$676.30	$676.20