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	$57.72	8.666%	$62.722	$62.72	$62.70	$62.70
Purchase #2	$167.85	8.455%	$182.0417	$182.04	$182.05	$182.00
Purchase #3	$199.66	5.417%	$210.4756	$210.48	$210.50	$210.50
Purchase #4	$168.40	11.302%	$187.4326	$187.43	$187.45	$187.40
Purchase #5	$237.59	12.595%	$267.5145	$267.51	$267.50	$267.50
Purchase #6	$233.64	13.363%	$264.8613	$264.86	$264.85	$264.90
Purchase #7	$81.84	4.507%	$85.5285	$85.53	$85.55	$85.50
7 purchase totals =	$1,146.70		$1,260.5762	$1,260.57	$1,260.60	$1,260.50