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	$64.54	12.740%	$72.7624	$72.76	$72.75	$72.80
Purchase #2	$109.64	3.483%	$113.4588	$113.46	$113.45	$113.50
Purchase #3	$48.92	5.614%	$51.6664	$51.67	$51.65	$51.70
Purchase #4	$246.37	7.735%	$265.4267	$265.43	$265.45	$265.40
Purchase #5	$107.27	8.167%	$116.0307	$116.03	$116.05	$116.00
Purchase #6	$238.85	8.598%	$259.3863	$259.39	$259.40	$259.40
Purchase #7	$59.56	5.532%	$62.8549	$62.85	$62.85	$62.90
7 purchase totals =	$875.15		$941.5862	$941.59	$941.60	$941.70