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	$218.27	7.745%	$235.175	$235.18	$235.20	$235.20
Purchase #2	$59.43	4.502%	$62.1055	$62.11	$62.10	$62.10
Purchase #3	$123.98	6.126%	$131.575	$131.58	$131.60	$131.60
Purchase #4	$157.55	4.583%	$164.7705	$164.77	$164.75	$164.80
Purchase #5	$197.47	7.594%	$212.4659	$212.47	$212.45	$212.50
Purchase #6	$150.36	12.168%	$168.6558	$168.66	$168.65	$168.70
Purchase #7	$108.47	4.312%	$113.1472	$113.15	$113.15	$113.10
7 purchase totals =	$1,015.53		$1,087.8949	$1,087.92	$1,087.90	$1,088.00