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	$190.97	10.141%	$210.3363	$210.34	$210.35	$210.30
Purchase #2	$130.62	10.555%	$144.4069	$144.41	$144.40	$144.40
Purchase #3	$34.76	10.672%	$38.4696	$38.47	$38.45	$38.50
Purchase #4	$45.57	3.154%	$47.0073	$47.01	$47.00	$47.00
Purchase #5	$114.49	5.492%	$120.7778	$120.78	$120.80	$120.80
Purchase #6	$178.33	10.214%	$196.5446	$196.54	$196.55	$196.50
Purchase #7	$161.94	7.447%	$173.9997	$174.00	$174.00	$174.00
7 purchase totals =	$856.68		$931.5422	$931.55	$931.55	$931.50