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	$179.26	11.286%	$199.4913	$199.49	$199.50	$199.50
Purchase #2	$114.61	4.708%	$120.0058	$120.01	$120.00	$120.00
Purchase #3	$243.31	9.105%	$265.4634	$265.46	$265.45	$265.50
Purchase #4	$192.68	13.807%	$219.2833	$219.28	$219.30	$219.30
Purchase #5	$67.66	12.498%	$76.1161	$76.12	$76.10	$76.10
Purchase #6	$108.91	13.862%	$124.0071	$124.01	$124.00	$124.00
Purchase #7	$33.90	13.620%	$38.5172	$38.52	$38.50	$38.50
7 purchase totals =	$940.33		$1,042.8842	$1,042.89	$1,042.85	$1,042.90