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	$13.70	8.709%	$14.8931	$14.89	$14.90	$14.90
Purchase #2	$110.69	11.698%	$123.6385	$123.64	$123.65	$123.60
Purchase #3	$221.27	11.558%	$246.8444	$246.84	$246.85	$246.80
Purchase #4	$232.65	11.764%	$260.0189	$260.02	$260.00	$260.00
Purchase #5	$217.38	11.145%	$241.607	$241.61	$241.60	$241.60
Purchase #6	$56.44	8.741%	$61.3734	$61.37	$61.35	$61.40
Purchase #7	$133.48	13.830%	$151.9403	$151.94	$151.95	$151.90
7 purchase totals =	$985.61		$1,100.3156	$1,100.31	$1,100.30	$1,100.20