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	$85.40	13.604%	$97.0178	$97.02	$97.00	$97.00
Purchase #2	$72.75	7.683%	$78.3394	$78.34	$78.35	$78.30
Purchase #3	$148.81	5.316%	$156.7207	$156.72	$156.70	$156.70
Purchase #4	$241.79	9.711%	$265.2702	$265.27	$265.25	$265.30
Purchase #5	$102.81	10.748%	$113.86	$113.86	$113.85	$113.90
Purchase #6	$170.40	9.347%	$186.3273	$186.33	$186.35	$186.30
Purchase #7	$190.73	5.624%	$201.4567	$201.46	$201.45	$201.50
7 purchase totals =	$1,012.69		$1,098.9921	$1,099.00	$1,098.95	$1,099.00