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	$62.66	7.356%	$67.2693	$67.27	$67.25	$67.30
Purchase #2	$37.37	3.538%	$38.6922	$38.69	$38.70	$38.70
Purchase #3	$147.87	13.540%	$167.8916	$167.89	$167.90	$167.90
Purchase #4	$121.63	5.379%	$128.1725	$128.17	$128.15	$128.20
Purchase #5	$90.64	9.269%	$99.0414	$99.04	$99.05	$99.00
Purchase #6	$71.81	9.769%	$78.8251	$78.83	$78.85	$78.80
Purchase #7	$80.49	5.834%	$85.1858	$85.19	$85.20	$85.20
7 purchase totals =	$612.47		$665.0779	$665.08	$665.10	$665.10