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	$224.54	10.299%	$247.6654	$247.67	$247.65	$247.70
Purchase #2	$188.27	4.428%	$196.6066	$196.61	$196.60	$196.60
Purchase #3	$62.79	13.474%	$71.2503	$71.25	$71.25	$71.30
Purchase #4	$130.68	9.793%	$143.4775	$143.48	$143.50	$143.50
Purchase #5	$168.39	4.262%	$175.5668	$175.57	$175.55	$175.60
Purchase #6	$122.47	13.535%	$139.0463	$139.05	$139.05	$139.00
Purchase #7	$220.36	7.766%	$237.4732	$237.47	$237.45	$237.50
7 purchase totals =	$1,117.50		$1,211.0861	$1,211.10	$1,211.05	$1,211.20