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	$134.53	4.410%	$140.4628	$140.46	$140.45	$140.50
Purchase #2	$149.98	3.209%	$154.7929	$154.79	$154.80	$154.80
Purchase #3	$189.70	3.306%	$195.9715	$195.97	$195.95	$196.00
Purchase #4	$116.42	9.340%	$127.2936	$127.29	$127.30	$127.30
Purchase #5	$190.66	4.488%	$199.2168	$199.22	$199.20	$199.20
Purchase #6	$50.56	7.800%	$54.5037	$54.50	$54.50	$54.50
Purchase #7	$80.68	5.488%	$85.1077	$85.11	$85.10	$85.10
7 purchase totals =	$912.53		$957.3490	$957.34	$957.30	$957.40