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	$51.79	7.121%	$55.478	$55.48	$55.50	$55.50
Purchase #2	$56.39	6.162%	$59.8648	$59.86	$59.85	$59.90
Purchase #3	$191.68	10.787%	$212.3565	$212.36	$212.35	$212.40
Purchase #4	$10.55	13.548%	$11.9793	$11.98	$12.00	$12.00
Purchase #5	$18.80	10.196%	$20.7168	$20.72	$20.70	$20.70
Purchase #6	$223.36	3.549%	$231.287	$231.29	$231.30	$231.30
Purchase #7	$156.85	9.297%	$171.4323	$171.43	$171.45	$171.40
7 purchase totals =	$709.42		$763.1147	$763.12	$763.15	$763.20