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	$214.70	4.853%	$225.1194	$225.12	$225.10	$225.10
Purchase #2	$15.37	13.166%	$17.3936	$17.39	$17.40	$17.40
Purchase #3	$206.62	3.155%	$213.1389	$213.14	$213.15	$213.10
Purchase #4	$91.56	8.193%	$99.0615	$99.06	$99.05	$99.10
Purchase #5	$137.41	9.593%	$150.5917	$150.59	$150.60	$150.60
Purchase #6	$145.56	7.733%	$156.8162	$156.82	$156.80	$156.80
Purchase #7	$145.33	9.297%	$158.8413	$158.84	$158.85	$158.80
7 purchase totals =	$956.55		$1,020.9626	$1,020.96	$1,020.95	$1,020.90