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	$228.86	3.229%	$236.2499	$236.25	$236.25	$236.20
Purchase #2	$124.56	3.401%	$128.7963	$128.80	$128.80	$128.80
Purchase #3	$161.26	11.196%	$179.3147	$179.31	$179.30	$179.30
Purchase #4	$160.53	11.221%	$178.5431	$178.54	$178.55	$178.50
Purchase #5	$116.83	11.641%	$130.4302	$130.43	$130.45	$130.40
Purchase #6	$19.39	6.364%	$20.624	$20.62	$20.60	$20.60
Purchase #7	$201.61	12.268%	$226.3435	$226.34	$226.35	$226.30
7 purchase totals =	$1,013.04		$1,100.3017	$1,100.29	$1,100.30	$1,100.10