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	$216.35	10.537%	$239.1468	$239.15	$239.15	$239.10
Purchase #2	$48.98	8.274%	$53.0326	$53.03	$53.05	$53.00
Purchase #3	$50.78	5.472%	$53.5587	$53.56	$53.55	$53.60
Purchase #4	$157.45	13.227%	$178.2759	$178.28	$178.30	$178.30
Purchase #5	$114.47	8.243%	$123.9058	$123.91	$123.90	$123.90
Purchase #6	$107.83	9.552%	$118.1299	$118.13	$118.15	$118.10
Purchase #7	$65.57	5.639%	$69.2675	$69.27	$69.25	$69.30
7 purchase totals =	$761.43		$835.3172	$835.33	$835.35	$835.30