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	$107.77	7.660%	$116.0252	$116.03	$116.05	$116.00
Purchase #2	$101.45	11.439%	$113.0549	$113.05	$113.05	$113.10
Purchase #3	$82.41	9.114%	$89.9208	$89.92	$89.90	$89.90
Purchase #4	$250.38	4.406%	$261.4117	$261.41	$261.40	$261.40
Purchase #5	$192.57	3.251%	$198.8305	$198.83	$198.85	$198.80
Purchase #6	$246.33	4.314%	$256.9567	$256.96	$256.95	$257.00
Purchase #7	$27.68	13.446%	$31.4019	$31.40	$31.40	$31.40
7 purchase totals =	$1,008.59		$1,067.6017	$1,067.60	$1,067.60	$1,067.60