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	$31.36	12.386%	$35.2442	$35.24	$35.25	$35.20
Purchase #2	$64.83	13.595%	$73.6436	$73.64	$73.65	$73.60
Purchase #3	$107.54	6.439%	$114.4645	$114.46	$114.45	$114.50
Purchase #4	$243.93	12.239%	$273.7846	$273.78	$273.80	$273.80
Purchase #5	$88.58	10.869%	$98.2078	$98.21	$98.20	$98.20
Purchase #6	$215.83	12.874%	$243.616	$243.62	$243.60	$243.60
Purchase #7	$250.32	13.729%	$284.6864	$284.69	$284.70	$284.70
7 purchase totals =	$1,002.39		$1,123.6471	$1,123.64	$1,123.65	$1,123.60