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	$179.85	11.351%	$200.2648	$200.26	$200.25	$200.30
Purchase #2	$94.34	5.557%	$99.5825	$99.58	$99.60	$99.60
Purchase #3	$240.94	3.806%	$250.1102	$250.11	$250.10	$250.10
Purchase #4	$244.28	10.544%	$270.0369	$270.04	$270.05	$270.00
Purchase #5	$227.57	4.282%	$237.3145	$237.31	$237.30	$237.30
Purchase #6	$18.31	4.564%	$19.1457	$19.15	$19.15	$19.10
Purchase #7	$14.45	11.845%	$16.1616	$16.16	$16.15	$16.20
7 purchase totals =	$1,019.74		$1,092.6162	$1,092.61	$1,092.60	$1,092.60