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	$108.32	5.616%	$114.4033	$114.40	$114.40	$114.40
Purchase #2	$173.71	6.316%	$184.6815	$184.68	$184.70	$184.70
Purchase #3	$124.75	3.112%	$128.6322	$128.63	$128.65	$128.60
Purchase #4	$133.66	10.260%	$147.3735	$147.37	$147.35	$147.40
Purchase #5	$216.38	5.217%	$227.6685	$227.67	$227.65	$227.70
Purchase #6	$65.44	11.370%	$72.8805	$72.88	$72.90	$72.90
Purchase #7	$86.27	4.136%	$89.8381	$89.84	$89.85	$89.80
7 purchase totals =	$908.53		$965.4776	$965.47	$965.50	$965.50