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	$236.78	5.775%	$250.454	$250.45	$250.45	$250.50
Purchase #2	$123.29	6.594%	$131.4197	$131.42	$131.40	$131.40
Purchase #3	$81.51	5.170%	$85.7241	$85.72	$85.70	$85.70
Purchase #4	$127.94	4.320%	$133.467	$133.47	$133.45	$133.50
Purchase #5	$84.48	8.282%	$91.4766	$91.48	$91.50	$91.50
Purchase #6	$155.58	7.596%	$167.3979	$167.40	$167.40	$167.40
Purchase #7	$173.50	6.251%	$184.3455	$184.35	$184.35	$184.30
7 purchase totals =	$983.08		$1,044.2848	$1,044.29	$1,044.25	$1,044.30