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	$198.26	11.624%	$221.3057	$221.31	$221.30	$221.30
Purchase #2	$56.36	13.308%	$63.8604	$63.86	$63.85	$63.90
Purchase #3	$26.41	6.376%	$28.0939	$28.09	$28.10	$28.10
Purchase #4	$152.60	11.355%	$169.9277	$169.93	$169.95	$169.90
Purchase #5	$123.88	6.462%	$131.8851	$131.89	$131.90	$131.90
Purchase #6	$50.34	3.429%	$52.0662	$52.07	$52.05	$52.10
Purchase #7	$137.39	13.245%	$155.5873	$155.59	$155.60	$155.60
7 purchase totals =	$745.24		$822.7263	$822.74	$822.75	$822.80