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	$67.49	6.655%	$71.9815	$71.98	$72.00	$72.00
Purchase #2	$109.31	4.248%	$113.9535	$113.95	$113.95	$114.00
Purchase #3	$200.73	12.357%	$225.5342	$225.53	$225.55	$225.50
Purchase #4	$111.80	10.870%	$123.9527	$123.95	$123.95	$124.00
Purchase #5	$53.31	13.838%	$60.687	$60.69	$60.70	$60.70
Purchase #6	$95.90	12.189%	$107.5893	$107.59	$107.60	$107.60
Purchase #7	$30.98	6.122%	$32.8766	$32.88	$32.90	$32.90
7 purchase totals =	$669.52		$736.5748	$736.57	$736.65	$736.70