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	$114.58	12.458%	$128.8544	$128.85	$128.85	$128.90
Purchase #2	$16.99	9.548%	$18.6122	$18.61	$18.60	$18.60
Purchase #3	$83.46	5.811%	$88.3099	$88.31	$88.30	$88.30
Purchase #4	$227.45	13.796%	$258.829	$258.83	$258.85	$258.80
Purchase #5	$198.39	12.673%	$223.532	$223.53	$223.55	$223.50
Purchase #6	$100.44	3.456%	$103.9112	$103.91	$103.90	$103.90
Purchase #7	$183.57	13.557%	$208.4566	$208.46	$208.45	$208.50
7 purchase totals =	$924.88		$1,030.5053	$1,030.50	$1,030.50	$1,030.50