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	$168.73	13.717%	$191.8747	$191.87	$191.85	$191.90
Purchase #2	$229.35	13.279%	$259.8054	$259.81	$259.80	$259.80
Purchase #3	$95.58	10.220%	$105.3483	$105.35	$105.35	$105.30
Purchase #4	$236.60	8.493%	$256.6944	$256.69	$256.70	$256.70
Purchase #5	$88.81	13.399%	$100.7097	$100.71	$100.70	$100.70
Purchase #6	$78.94	10.818%	$87.4797	$87.48	$87.50	$87.50
Purchase #7	$122.49	13.141%	$138.5864	$138.59	$138.60	$138.60
7 purchase totals =	$1,020.50		$1,140.4986	$1,140.50	$1,140.50	$1,140.50