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	$71.92	9.199%	$78.5359	$78.54	$78.55	$78.50
Purchase #2	$182.47	13.849%	$207.7403	$207.74	$207.75	$207.70
Purchase #3	$99.70	3.128%	$102.8186	$102.82	$102.80	$102.80
Purchase #4	$209.34	3.729%	$217.1463	$217.15	$217.15	$217.10
Purchase #5	$52.89	11.825%	$59.1442	$59.14	$59.15	$59.10
Purchase #6	$207.78	8.315%	$225.0569	$225.06	$225.05	$225.10
Purchase #7	$230.35	11.554%	$256.9646	$256.96	$256.95	$257.00
7 purchase totals =	$1,054.45		$1,147.4068	$1,147.41	$1,147.40	$1,147.30