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	$45.39	4.285%	$47.335	$47.34	$47.35	$47.30
Purchase #2	$234.51	12.789%	$264.5015	$264.50	$264.50	$264.50
Purchase #3	$156.76	8.253%	$169.6974	$169.70	$169.70	$169.70
Purchase #4	$166.71	8.398%	$180.7103	$180.71	$180.70	$180.70
Purchase #5	$68.33	6.426%	$72.7209	$72.72	$72.70	$72.70
Purchase #6	$137.56	4.661%	$143.9717	$143.97	$143.95	$144.00
Purchase #7	$42.92	13.240%	$48.6026	$48.60	$48.60	$48.60
7 purchase totals =	$852.18		$927.5394	$927.54	$927.50	$927.50