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	$81.59	4.276%	$85.0788	$85.08	$85.10	$85.10
Purchase #2	$180.74	11.128%	$200.8527	$200.85	$200.85	$200.90
Purchase #3	$24.71	4.597%	$25.8459	$25.85	$25.85	$25.80
Purchase #4	$92.70	5.218%	$97.5371	$97.54	$97.55	$97.50
Purchase #5	$137.82	4.427%	$143.9213	$143.92	$143.90	$143.90
Purchase #6	$236.39	12.419%	$265.7473	$265.75	$265.75	$265.70
Purchase #7	$141.53	6.313%	$150.4648	$150.46	$150.45	$150.50
7 purchase totals =	$895.48		$969.4479	$969.45	$969.45	$969.40