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	$13.70	8.480%	$14.8618	$14.86	$14.85	$14.90
Purchase #2	$179.56	11.629%	$200.441	$200.44	$200.45	$200.40
Purchase #3	$151.59	13.524%	$172.091	$172.09	$172.10	$172.10
Purchase #4	$65.67	9.259%	$71.7504	$71.75	$71.75	$71.80
Purchase #5	$88.68	6.292%	$94.2597	$94.26	$94.25	$94.30
Purchase #6	$37.79	11.777%	$42.2405	$42.24	$42.25	$42.20
Purchase #7	$122.54	9.650%	$134.3651	$134.37	$134.35	$134.40
7 purchase totals =	$659.53		$730.0095	$730.01	$730.00	$730.10