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	$43.51	6.291%	$46.2472	$46.25	$46.25	$46.20
Purchase #2	$128.65	12.615%	$144.8792	$144.88	$144.90	$144.90
Purchase #3	$100.48	5.219%	$105.7241	$105.72	$105.70	$105.70
Purchase #4	$142.63	9.205%	$155.7591	$155.76	$155.75	$155.80
Purchase #5	$86.67	13.800%	$98.6305	$98.63	$98.65	$98.60
Purchase #6	$231.58	9.449%	$253.462	$253.46	$253.45	$253.50
Purchase #7	$112.99	12.362%	$126.9578	$126.96	$126.95	$127.00
7 purchase totals =	$846.51		$931.6599	$931.66	$931.65	$931.70