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	$163.70	5.539%	$172.7673	$172.77	$172.75	$172.80
Purchase #2	$138.98	8.123%	$150.2693	$150.27	$150.25	$150.30
Purchase #3	$33.76	11.614%	$37.6809	$37.68	$37.70	$37.70
Purchase #4	$250.86	9.851%	$275.5722	$275.57	$275.55	$275.60
Purchase #5	$160.73	12.591%	$180.9675	$180.97	$180.95	$181.00
Purchase #6	$130.86	13.514%	$148.5444	$148.54	$148.55	$148.50
Purchase #7	$197.60	9.318%	$216.0124	$216.01	$216.00	$216.00
7 purchase totals =	$1,076.49		$1,181.8140	$1,181.81	$1,181.75	$1,181.90