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	$58.52	8.597%	$63.551	$63.55	$63.55	$63.60
Purchase #2	$118.93	10.536%	$131.4605	$131.46	$131.45	$131.50
Purchase #3	$228.82	9.512%	$250.5854	$250.59	$250.60	$250.60
Purchase #4	$12.41	6.753%	$13.248	$13.25	$13.25	$13.20
Purchase #5	$120.90	4.613%	$126.4771	$126.48	$126.50	$126.50
Purchase #6	$131.96	7.637%	$142.0378	$142.04	$142.05	$142.00
Purchase #7	$29.49	12.744%	$33.2482	$33.25	$33.25	$33.20
7 purchase totals =	$701.03		$760.6080	$760.62	$760.65	$760.60