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	$239.42	5.813%	$253.3375	$253.34	$253.35	$253.30
Purchase #2	$225.39	3.474%	$233.22	$233.22	$233.20	$233.20
Purchase #3	$176.44	11.443%	$196.63	$196.63	$196.65	$196.60
Purchase #4	$159.96	5.497%	$168.753	$168.75	$168.75	$168.80
Purchase #5	$245.43	10.749%	$271.8113	$271.81	$271.80	$271.80
Purchase #6	$138.56	8.660%	$150.5593	$150.56	$150.55	$150.60
Purchase #7	$77.98	3.605%	$80.7912	$80.79	$80.80	$80.80
7 purchase totals =	$1,263.18		$1,355.1023	$1,355.10	$1,355.10	$1,355.10