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	$65.46	7.575%	$70.4186	$70.42	$70.40	$70.40
Purchase #2	$238.51	7.157%	$255.5802	$255.58	$255.60	$255.60
Purchase #3	$194.65	12.231%	$218.4576	$218.46	$218.45	$218.50
Purchase #4	$162.32	6.817%	$173.3854	$173.39	$173.40	$173.40
Purchase #5	$196.98	8.309%	$213.3471	$213.35	$213.35	$213.30
Purchase #6	$174.60	8.218%	$188.9486	$188.95	$188.95	$188.90
Purchase #7	$87.63	8.610%	$95.1749	$95.17	$95.15	$95.20
7 purchase totals =	$1,120.15		$1,215.3124	$1,215.32	$1,215.30	$1,215.30