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	$216.39	8.807%	$235.4475	$235.45	$235.45	$235.40
Purchase #2	$118.68	13.378%	$134.557	$134.56	$134.55	$134.60
Purchase #3	$10.45	3.131%	$10.7772	$10.78	$10.80	$10.80
Purchase #4	$242.75	12.639%	$273.4312	$273.43	$273.45	$273.40
Purchase #5	$141.72	7.623%	$152.5233	$152.52	$152.50	$152.50
Purchase #6	$83.34	6.820%	$89.0238	$89.02	$89.00	$89.00
Purchase #7	$235.72	6.260%	$250.4761	$250.48	$250.50	$250.50
7 purchase totals =	$1,049.05		$1,146.2361	$1,146.24	$1,146.25	$1,146.20