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	$128.63	13.560%	$146.0722	$146.07	$146.05	$146.10
Purchase #2	$39.56	13.173%	$44.7712	$44.77	$44.75	$44.80
Purchase #3	$250.27	7.491%	$269.0177	$269.02	$269.00	$269.00
Purchase #4	$181.65	11.105%	$201.8222	$201.82	$201.80	$201.80
Purchase #5	$83.88	6.314%	$89.1762	$89.18	$89.20	$89.20
Purchase #6	$106.45	9.838%	$116.9226	$116.92	$116.90	$116.90
Purchase #7	$173.91	13.102%	$196.6957	$196.70	$196.70	$196.70
7 purchase totals =	$964.35		$1,064.4778	$1,064.48	$1,064.40	$1,064.50