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	$33.38	6.149%	$35.4325	$35.43	$35.45	$35.40
Purchase #2	$83.98	4.219%	$87.5231	$87.52	$87.50	$87.50
Purchase #3	$127.64	7.289%	$136.9437	$136.94	$136.95	$136.90
Purchase #4	$82.25	8.832%	$89.5143	$89.51	$89.50	$89.50
Purchase #5	$85.47	4.208%	$89.0666	$89.07	$89.05	$89.10
Purchase #6	$87.37	5.632%	$92.2907	$92.29	$92.30	$92.30
Purchase #7	$154.67	7.777%	$166.6987	$166.70	$166.70	$166.70
7 purchase totals =	$654.76		$697.4696	$697.46	$697.45	$697.40