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	$6.74	4.730%	$7.0588	$7.06	$7.05	$7.10
Purchase #2	$149.65	7.302%	$160.5774	$160.58	$160.60	$160.60
Purchase #3	$248.58	8.435%	$269.5477	$269.55	$269.55	$269.50
Purchase #4	$248.47	6.669%	$265.0405	$265.04	$265.05	$265.00
Purchase #5	$85.63	5.381%	$90.2378	$90.24	$90.25	$90.20
Purchase #6	$89.28	13.487%	$101.3212	$101.32	$101.30	$101.30
Purchase #7	$227.53	11.867%	$254.531	$254.53	$254.55	$254.50
7 purchase totals =	$1,055.88		$1,148.3144	$1,148.32	$1,148.35	$1,148.20