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	$84.66	10.297%	$93.3774	$93.38	$93.40	$93.40
Purchase #2	$166.88	5.264%	$175.6646	$175.66	$175.65	$175.70
Purchase #3	$67.53	9.667%	$74.0581	$74.06	$74.05	$74.10
Purchase #4	$137.75	6.314%	$146.4475	$146.45	$146.45	$146.40
Purchase #5	$200.50	7.704%	$215.9465	$215.95	$215.95	$215.90
Purchase #6	$86.37	3.516%	$89.4068	$89.41	$89.40	$89.40
Purchase #7	$154.28	11.649%	$172.2521	$172.25	$172.25	$172.30
7 purchase totals =	$897.97		$967.1530	$967.16	$967.15	$967.20