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	$50.72	10.604%	$56.0983	$56.10	$56.10	$56.10
Purchase #2	$56.97	4.604%	$59.5929	$59.59	$59.60	$59.60
Purchase #3	$227.86	4.488%	$238.0864	$238.09	$238.10	$238.10
Purchase #4	$67.54	7.434%	$72.5609	$72.56	$72.55	$72.60
Purchase #5	$33.42	3.315%	$34.5279	$34.53	$34.55	$34.50
Purchase #6	$19.77	13.197%	$22.379	$22.38	$22.40	$22.40
Purchase #7	$195.79	10.801%	$216.9373	$216.94	$216.95	$216.90
7 purchase totals =	$652.07		$700.1827	$700.19	$700.25	$700.20