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	$237.72	8.733%	$258.4801	$258.48	$258.50	$258.50
Purchase #2	$76.63	7.780%	$82.5918	$82.59	$82.60	$82.60
Purchase #3	$101.77	9.316%	$111.2509	$111.25	$111.25	$111.30
Purchase #4	$21.75	4.872%	$22.8097	$22.81	$22.80	$22.80
Purchase #5	$187.46	13.808%	$213.3445	$213.34	$213.35	$213.30
Purchase #6	$87.56	12.317%	$98.3448	$98.34	$98.35	$98.30
Purchase #7	$133.29	3.218%	$137.5793	$137.58	$137.60	$137.60
7 purchase totals =	$846.18		$924.4011	$924.39	$924.45	$924.40