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	$244.78	12.536%	$275.4656	$275.47	$275.45	$275.50
Purchase #2	$88.34	12.564%	$99.439	$99.44	$99.45	$99.40
Purchase #3	$42.69	10.647%	$47.2352	$47.24	$47.25	$47.20
Purchase #4	$147.88	13.739%	$168.1972	$168.20	$168.20	$168.20
Purchase #5	$199.28	13.710%	$226.6013	$226.60	$226.60	$226.60
Purchase #6	$133.29	5.393%	$140.4783	$140.48	$140.50	$140.50
Purchase #7	$135.60	10.806%	$150.2529	$150.25	$150.25	$150.30
7 purchase totals =	$991.86		$1,107.6695	$1,107.68	$1,107.70	$1,107.70