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	$153.43	7.458%	$164.8728	$164.87	$164.85	$164.90
Purchase #2	$98.40	10.816%	$109.0429	$109.04	$109.05	$109.00
Purchase #3	$192.97	8.245%	$208.8804	$208.88	$208.90	$208.90
Purchase #4	$166.58	12.456%	$187.3292	$187.33	$187.35	$187.30
Purchase #5	$71.29	3.478%	$73.7695	$73.77	$73.75	$73.80
Purchase #6	$141.34	3.672%	$146.53	$146.53	$146.55	$146.50
Purchase #7	$112.58	13.825%	$128.1442	$128.14	$128.15	$128.10
7 purchase totals =	$936.59		$1,018.5690	$1,018.56	$1,018.60	$1,018.50