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	$159.44	13.343%	$180.7141	$180.71	$180.70	$180.70
Purchase #2	$236.93	13.714%	$269.4226	$269.42	$269.40	$269.40
Purchase #3	$159.75	12.628%	$179.9232	$179.92	$179.90	$179.90
Purchase #4	$39.32	3.109%	$40.5425	$40.54	$40.55	$40.50
Purchase #5	$189.96	4.394%	$198.3068	$198.31	$198.30	$198.30
Purchase #6	$127.75	9.201%	$139.5043	$139.50	$139.50	$139.50
Purchase #7	$92.48	7.300%	$99.231	$99.23	$99.25	$99.20
7 purchase totals =	$1,005.63		$1,107.6445	$1,107.63	$1,107.60	$1,107.50