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	$105.80	7.369%	$113.5964	$113.60	$113.60	$113.60
Purchase #2	$206.29	4.374%	$215.3131	$215.31	$215.30	$215.30
Purchase #3	$9.70	13.741%	$11.0329	$11.03	$11.05	$11.00
Purchase #4	$246.27	11.673%	$275.0171	$275.02	$275.00	$275.00
Purchase #5	$126.59	4.541%	$132.3385	$132.34	$132.35	$132.30
Purchase #6	$117.78	7.113%	$126.1577	$126.16	$126.15	$126.20
Purchase #7	$188.39	4.109%	$196.1309	$196.13	$196.15	$196.10
7 purchase totals =	$1,000.82		$1,069.5866	$1,069.59	$1,069.60	$1,069.50