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	$100.57	5.228%	$105.8278	$105.83	$105.85	$105.80
Purchase #2	$10.58	8.121%	$11.4392	$11.44	$11.45	$11.40
Purchase #3	$104.26	7.824%	$112.4173	$112.42	$112.40	$112.40
Purchase #4	$78.72	13.642%	$89.459	$89.46	$89.45	$89.50
Purchase #5	$209.34	5.726%	$221.3268	$221.33	$221.35	$221.30
Purchase #6	$91.52	3.690%	$94.8971	$94.90	$94.90	$94.90
Purchase #7	$223.35	10.853%	$247.5902	$247.59	$247.60	$247.60
7 purchase totals =	$818.34		$882.9574	$882.97	$883.00	$882.90