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	$101.88	12.287%	$114.398	$114.40	$114.40	$114.40
Purchase #2	$162.31	4.437%	$169.5117	$169.51	$169.50	$169.50
Purchase #3	$41.81	9.798%	$45.9065	$45.91	$45.90	$45.90
Purchase #4	$98.79	13.603%	$112.2284	$112.23	$112.25	$112.20
Purchase #5	$245.89	12.632%	$276.9508	$276.95	$276.95	$277.00
Purchase #6	$145.95	12.378%	$164.0157	$164.02	$164.00	$164.00
Purchase #7	$9.86	10.227%	$10.8684	$10.87	$10.85	$10.90
7 purchase totals =	$806.49		$893.8795	$893.89	$893.85	$893.90