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	$46.89	10.247%	$51.6948	$51.69	$51.70	$51.70
Purchase #2	$206.43	8.438%	$223.8486	$223.85	$223.85	$223.80
Purchase #3	$185.76	10.637%	$205.5193	$205.52	$205.50	$205.50
Purchase #4	$29.80	13.851%	$33.9276	$33.93	$33.95	$33.90
Purchase #5	$167.71	9.873%	$184.268	$184.27	$184.25	$184.30
Purchase #6	$120.47	9.470%	$131.8785	$131.88	$131.90	$131.90
Purchase #7	$171.80	11.620%	$191.7632	$191.76	$191.75	$191.80
7 purchase totals =	$928.86		$1,022.9000	$1,022.90	$1,022.90	$1,022.90