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	$67.31	8.103%	$72.7641	$72.76	$72.75	$72.80
Purchase #2	$214.74	10.246%	$236.7423	$236.74	$236.75	$236.70
Purchase #3	$86.76	3.130%	$89.4756	$89.48	$89.50	$89.50
Purchase #4	$45.32	5.821%	$47.9581	$47.96	$47.95	$48.00
Purchase #5	$170.38	12.360%	$191.439	$191.44	$191.45	$191.40
Purchase #6	$78.86	7.711%	$84.9409	$84.94	$84.95	$84.90
Purchase #7	$128.61	13.823%	$146.3878	$146.39	$146.40	$146.40
7 purchase totals =	$791.98		$869.7078	$869.71	$869.75	$869.70