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	$82.76	3.684%	$85.8089	$85.81	$85.80	$85.80
Purchase #2	$134.42	7.724%	$144.8026	$144.80	$144.80	$144.80
Purchase #3	$229.99	8.706%	$250.0129	$250.01	$250.00	$250.00
Purchase #4	$131.86	10.363%	$145.5247	$145.52	$145.50	$145.50
Purchase #5	$232.33	4.144%	$241.9578	$241.96	$241.95	$242.00
Purchase #6	$119.88	7.400%	$128.7511	$128.75	$128.75	$128.80
Purchase #7	$103.57	4.333%	$108.0577	$108.06	$108.05	$108.10
7 purchase totals =	$1,034.81		$1,104.9157	$1,104.91	$1,104.85	$1,105.00