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	$245.30	4.290%	$255.8234	$255.82	$255.80	$255.80
Purchase #2	$125.95	11.197%	$140.0526	$140.05	$140.05	$140.10
Purchase #3	$148.83	7.606%	$160.15	$160.15	$160.15	$160.20
Purchase #4	$39.91	13.346%	$45.2364	$45.24	$45.25	$45.20
Purchase #5	$145.65	3.642%	$150.9546	$150.95	$150.95	$151.00
Purchase #6	$95.29	9.268%	$104.1215	$104.12	$104.10	$104.10
Purchase #7	$136.38	8.767%	$148.3364	$148.34	$148.35	$148.30
7 purchase totals =	$937.31		$1,004.6749	$1,004.67	$1,004.65	$1,004.70