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	$58.32	12.118%	$65.3872	$65.39	$65.40	$65.40
Purchase #2	$113.86	12.251%	$127.809	$127.81	$127.80	$127.80
Purchase #3	$179.68	9.403%	$196.5753	$196.58	$196.60	$196.60
Purchase #4	$100.92	4.448%	$105.4089	$105.41	$105.40	$105.40
Purchase #5	$73.88	12.289%	$82.9591	$82.96	$82.95	$83.00
Purchase #6	$124.76	13.376%	$141.4479	$141.45	$141.45	$141.40
Purchase #7	$195.50	10.698%	$216.4146	$216.41	$216.40	$216.40
7 purchase totals =	$846.92		$936.0020	$936.01	$936.00	$936.00