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	$113.82	10.540%	$125.8166	$125.82	$125.80	$125.80
Purchase #2	$235.40	13.188%	$266.4446	$266.44	$266.45	$266.40
Purchase #3	$107.32	6.134%	$113.903	$113.90	$113.90	$113.90
Purchase #4	$64.27	10.387%	$70.9457	$70.95	$70.95	$70.90
Purchase #5	$85.76	4.178%	$89.3431	$89.34	$89.35	$89.30
Purchase #6	$89.81	11.317%	$99.9738	$99.97	$99.95	$100.00
Purchase #7	$131.62	5.712%	$139.1381	$139.14	$139.15	$139.10
7 purchase totals =	$828.00		$905.5649	$905.56	$905.55	$905.40