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	$223.82	10.297%	$246.8667	$246.87	$246.85	$246.90
Purchase #2	$169.90	6.245%	$180.5103	$180.51	$180.50	$180.50
Purchase #3	$79.91	9.493%	$87.4959	$87.50	$87.50	$87.50
Purchase #4	$18.96	4.456%	$19.8049	$19.80	$19.80	$19.80
Purchase #5	$130.31	5.308%	$137.2269	$137.23	$137.25	$137.20
Purchase #6	$137.53	6.803%	$146.8862	$146.89	$146.90	$146.90
Purchase #7	$199.98	7.821%	$215.6204	$215.62	$215.60	$215.60
7 purchase totals =	$960.41		$1,034.4113	$1,034.42	$1,034.40	$1,034.40