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	$197.36	6.136%	$209.47	$209.47	$209.45	$209.50
Purchase #2	$164.51	11.712%	$183.7774	$183.78	$183.80	$183.80
Purchase #3	$236.49	7.238%	$253.6071	$253.61	$253.60	$253.60
Purchase #4	$89.26	10.782%	$98.884	$98.88	$98.90	$98.90
Purchase #5	$55.38	10.334%	$61.103	$61.10	$61.10	$61.10
Purchase #6	$43.51	5.721%	$45.9992	$46.00	$46.00	$46.00
Purchase #7	$222.40	13.145%	$251.6345	$251.63	$251.65	$251.60
7 purchase totals =	$1,008.91		$1,104.4752	$1,104.47	$1,104.50	$1,104.50