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	$102.43	10.513%	$113.1985	$113.20	$113.20	$113.20
Purchase #2	$76.91	12.768%	$86.7299	$86.73	$86.75	$86.70
Purchase #3	$151.89	12.706%	$171.1891	$171.19	$171.20	$171.20
Purchase #4	$157.33	3.254%	$162.4495	$162.45	$162.45	$162.40
Purchase #5	$209.76	5.843%	$222.0163	$222.02	$222.00	$222.00
Purchase #6	$155.42	3.793%	$161.3151	$161.32	$161.30	$161.30
Purchase #7	$40.89	11.666%	$45.6602	$45.66	$45.65	$45.70
7 purchase totals =	$894.63		$962.5586	$962.57	$962.55	$962.50