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	$178.69	4.741%	$187.1617	$187.16	$187.15	$187.20
Purchase #2	$108.35	4.287%	$112.995	$113.00	$113.00	$113.00
Purchase #3	$72.53	13.819%	$82.5529	$82.55	$82.55	$82.60
Purchase #4	$140.76	4.140%	$146.5875	$146.59	$146.60	$146.60
Purchase #5	$203.38	10.675%	$225.0908	$225.09	$225.10	$225.10
Purchase #6	$192.66	13.617%	$218.8945	$218.89	$218.90	$218.90
Purchase #7	$204.53	11.449%	$227.9466	$227.95	$227.95	$227.90
7 purchase totals =	$1,100.90		$1,201.2290	$1,201.23	$1,201.25	$1,201.30