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	$48.28	9.104%	$52.6754	$52.68	$52.70	$52.70
Purchase #2	$72.27	8.742%	$78.5878	$78.59	$78.60	$78.60
Purchase #3	$230.81	10.649%	$255.389	$255.39	$255.40	$255.40
Purchase #4	$11.33	5.402%	$11.942	$11.94	$11.95	$11.90
Purchase #5	$165.33	12.379%	$185.7962	$185.80	$185.80	$185.80
Purchase #6	$42.84	6.381%	$45.5736	$45.57	$45.55	$45.60
Purchase #7	$136.86	3.515%	$141.6706	$141.67	$141.65	$141.70
7 purchase totals =	$707.72		$771.6346	$771.64	$771.65	$771.70