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	$192.93	3.423%	$199.534	$199.53	$199.55	$199.50
Purchase #2	$141.59	8.696%	$153.9027	$153.90	$153.90	$153.90
Purchase #3	$17.38	6.593%	$18.5259	$18.53	$18.55	$18.50
Purchase #4	$174.70	13.242%	$197.8338	$197.83	$197.85	$197.80
Purchase #5	$168.52	4.104%	$175.4361	$175.44	$175.45	$175.40
Purchase #6	$184.72	6.412%	$196.5642	$196.56	$196.55	$196.60
Purchase #7	$87.48	11.245%	$97.3171	$97.32	$97.30	$97.30
7 purchase totals =	$967.32		$1,039.1138	$1,039.11	$1,039.15	$1,039.00