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	$179.92	7.201%	$192.876	$192.88	$192.90	$192.90
Purchase #2	$117.68	7.712%	$126.7555	$126.76	$126.75	$126.80
Purchase #3	$179.92	9.363%	$196.7659	$196.77	$196.75	$196.80
Purchase #4	$162.82	10.482%	$179.8868	$179.89	$179.90	$179.90
Purchase #5	$86.84	13.261%	$98.3559	$98.36	$98.35	$98.40
Purchase #6	$56.66	8.360%	$61.3968	$61.40	$61.40	$61.40
Purchase #7	$87.93	8.618%	$95.5078	$95.51	$95.50	$95.50
7 purchase totals =	$871.77		$951.5447	$951.57	$951.55	$951.70