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	$207.40	10.391%	$228.9509	$228.95	$228.95	$229.00
Purchase #2	$67.56	7.589%	$72.6871	$72.69	$72.70	$72.70
Purchase #3	$93.97	6.643%	$100.2124	$100.21	$100.20	$100.20
Purchase #4	$246.84	7.319%	$264.9062	$264.91	$264.90	$264.90
Purchase #5	$140.28	8.770%	$152.5826	$152.58	$152.60	$152.60
Purchase #6	$192.79	12.307%	$216.5167	$216.52	$216.50	$216.50
Purchase #7	$242.28	13.538%	$275.0799	$275.08	$275.10	$275.10
7 purchase totals =	$1,191.12		$1,310.9358	$1,310.94	$1,310.95	$1,311.00