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	$128.47	10.279%	$141.6754	$141.68	$141.70	$141.70
Purchase #2	$106.95	9.131%	$116.7156	$116.72	$116.70	$116.70
Purchase #3	$93.95	7.420%	$100.9211	$100.92	$100.90	$100.90
Purchase #4	$209.68	4.853%	$219.8558	$219.86	$219.85	$219.90
Purchase #5	$80.79	13.157%	$91.4195	$91.42	$91.40	$91.40
Purchase #6	$236.52	8.163%	$255.8271	$255.83	$255.85	$255.80
Purchase #7	$165.39	9.505%	$181.1103	$181.11	$181.10	$181.10
7 purchase totals =	$1,021.75		$1,107.5248	$1,107.54	$1,107.50	$1,107.50