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	$48.67	13.145%	$55.0677	$55.07	$55.05	$55.10
Purchase #2	$54.40	12.824%	$61.3763	$61.38	$61.40	$61.40
Purchase #3	$83.81	12.327%	$94.1413	$94.14	$94.15	$94.10
Purchase #4	$91.58	8.199%	$99.0886	$99.09	$99.10	$99.10
Purchase #5	$40.65	7.140%	$43.5524	$43.55	$43.55	$43.60
Purchase #6	$106.40	12.742%	$119.9575	$119.96	$119.95	$120.00
Purchase #7	$69.99	4.697%	$73.2774	$73.28	$73.30	$73.30
7 purchase totals =	$495.50		$546.4612	$546.47	$546.50	$546.60