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	$170.32	6.519%	$181.4232	$181.42	$181.40	$181.40
Purchase #2	$213.56	8.866%	$232.4942	$232.49	$232.50	$232.50
Purchase #3	$105.72	5.692%	$111.7376	$111.74	$111.75	$111.70
Purchase #4	$150.67	3.822%	$156.4286	$156.43	$156.45	$156.40
Purchase #5	$158.49	8.192%	$171.4735	$171.47	$171.45	$171.50
Purchase #6	$168.68	8.281%	$182.6484	$182.65	$182.65	$182.60
Purchase #7	$124.47	9.531%	$136.3332	$136.33	$136.35	$136.30
7 purchase totals =	$1,091.91		$1,172.5387	$1,172.53	$1,172.55	$1,172.40