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	$218.89	11.247%	$243.5086	$243.51	$243.50	$243.50
Purchase #2	$97.57	13.869%	$111.102	$111.10	$111.10	$111.10
Purchase #3	$56.81	12.540%	$63.934	$63.93	$63.95	$63.90
Purchase #4	$226.52	11.162%	$251.8042	$251.80	$251.80	$251.80
Purchase #5	$201.94	7.800%	$217.6913	$217.69	$217.70	$217.70
Purchase #6	$46.27	9.626%	$50.724	$50.72	$50.70	$50.70
Purchase #7	$74.36	8.458%	$80.6494	$80.65	$80.65	$80.60
7 purchase totals =	$922.36		$1,019.4135	$1,019.40	$1,019.40	$1,019.30