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	$172.54	7.511%	$185.4995	$185.50	$185.50	$185.50
Purchase #2	$40.42	7.814%	$43.5784	$43.58	$43.60	$43.60
Purchase #3	$50.39	11.858%	$56.3652	$56.37	$56.35	$56.40
Purchase #4	$239.75	12.460%	$269.6229	$269.62	$269.60	$269.60
Purchase #5	$45.31	4.792%	$47.4813	$47.48	$47.50	$47.50
Purchase #6	$104.72	6.840%	$111.8828	$111.88	$111.90	$111.90
Purchase #7	$31.74	13.319%	$35.9675	$35.97	$35.95	$36.00
7 purchase totals =	$684.87		$750.3976	$750.40	$750.40	$750.50