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	$167.92	12.380%	$188.7085	$188.71	$188.70	$188.70
Purchase #2	$148.35	7.626%	$159.6632	$159.66	$159.65	$159.70
Purchase #3	$164.87	9.123%	$179.9111	$179.91	$179.90	$179.90
Purchase #4	$176.81	5.743%	$186.9642	$186.96	$186.95	$187.00
Purchase #5	$138.33	11.518%	$154.2628	$154.26	$154.25	$154.30
Purchase #6	$55.31	11.533%	$61.6889	$61.69	$61.70	$61.70
Purchase #7	$82.83	3.579%	$85.7945	$85.79	$85.80	$85.80
7 purchase totals =	$934.42		$1,016.9932	$1,016.98	$1,016.95	$1,017.10