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	$61.25	9.573%	$67.1135	$67.11	$67.10	$67.10
Purchase #2	$25.59	3.363%	$26.4506	$26.45	$26.45	$26.50
Purchase #3	$168.80	11.192%	$187.6921	$187.69	$187.70	$187.70
Purchase #4	$92.70	8.492%	$100.5721	$100.57	$100.55	$100.60
Purchase #5	$69.37	10.401%	$76.5852	$76.59	$76.60	$76.60
Purchase #6	$111.71	6.271%	$118.7153	$118.72	$118.70	$118.70
Purchase #7	$225.87	12.196%	$253.4171	$253.42	$253.40	$253.40
7 purchase totals =	$755.29		$830.5459	$830.55	$830.50	$830.60