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	$231.57	13.192%	$262.1187	$262.12	$262.10	$262.10
Purchase #2	$76.34	7.697%	$82.2159	$82.22	$82.20	$82.20
Purchase #3	$141.59	4.534%	$148.0097	$148.01	$148.00	$148.00
Purchase #4	$239.97	11.444%	$267.4322	$267.43	$267.45	$267.40
Purchase #5	$135.46	11.520%	$151.065	$151.07	$151.05	$151.10
Purchase #6	$67.34	7.341%	$72.2834	$72.28	$72.30	$72.30
Purchase #7	$133.74	13.527%	$151.831	$151.83	$151.85	$151.80
7 purchase totals =	$1,026.01		$1,134.9559	$1,134.96	$1,134.95	$1,134.90