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	$81.64	4.244%	$85.1048	$85.10	$85.10	$85.10
Purchase #2	$219.48	8.457%	$238.0414	$238.04	$238.05	$238.00
Purchase #3	$42.85	13.667%	$48.7063	$48.71	$48.70	$48.70
Purchase #4	$114.86	8.467%	$124.5852	$124.59	$124.60	$124.60
Purchase #5	$210.56	8.123%	$227.6638	$227.66	$227.65	$227.70
Purchase #6	$181.69	10.593%	$200.9364	$200.94	$200.95	$200.90
Purchase #7	$78.66	11.390%	$87.6194	$87.62	$87.60	$87.60
7 purchase totals =	$929.74		$1,012.6573	$1,012.66	$1,012.65	$1,012.60