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	$53.93	12.239%	$60.5305	$60.53	$60.55	$60.50
Purchase #2	$177.62	12.849%	$200.4424	$200.44	$200.45	$200.40
Purchase #3	$244.34	9.709%	$268.063	$268.06	$268.05	$268.10
Purchase #4	$157.57	6.458%	$167.7459	$167.75	$167.75	$167.70
Purchase #5	$167.37	3.265%	$172.8346	$172.83	$172.85	$172.80
Purchase #6	$41.49	10.442%	$45.8224	$45.82	$45.80	$45.80
Purchase #7	$5.69	3.442%	$5.8858	$5.89	$5.90	$5.90
7 purchase totals =	$848.01		$921.3246	$921.32	$921.35	$921.20