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	$237.49	12.663%	$267.5634	$267.56	$267.55	$267.60
Purchase #2	$66.95	6.371%	$71.2154	$71.22	$71.20	$71.20
Purchase #3	$47.72	13.734%	$54.2739	$54.27	$54.25	$54.30
Purchase #4	$189.80	11.343%	$211.329	$211.33	$211.35	$211.30
Purchase #5	$154.78	8.628%	$168.1344	$168.13	$168.15	$168.10
Purchase #6	$49.72	6.680%	$53.0413	$53.04	$53.05	$53.00
Purchase #7	$129.36	5.168%	$136.0453	$136.05	$136.05	$136.00
7 purchase totals =	$875.82		$961.6027	$961.60	$961.60	$961.50