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	$154.36	4.841%	$161.8326	$161.83	$161.85	$161.80
Purchase #2	$168.76	4.581%	$176.4909	$176.49	$176.50	$176.50
Purchase #3	$245.98	4.498%	$257.0442	$257.04	$257.05	$257.00
Purchase #4	$91.58	9.777%	$100.5338	$100.53	$100.55	$100.50
Purchase #5	$107.43	3.760%	$111.4694	$111.47	$111.45	$111.50
Purchase #6	$102.59	6.779%	$109.5446	$109.54	$109.55	$109.50
Purchase #7	$13.61	6.732%	$14.5262	$14.53	$14.55	$14.50
7 purchase totals =	$884.31		$931.4417	$931.43	$931.50	$931.30