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	$111.50	13.829%	$126.9193	$126.92	$126.90	$126.90
Purchase #2	$224.55	6.744%	$239.6937	$239.69	$239.70	$239.70
Purchase #3	$31.48	4.862%	$33.0106	$33.01	$33.00	$33.00
Purchase #4	$34.78	12.198%	$39.0225	$39.02	$39.00	$39.00
Purchase #5	$5.54	3.310%	$5.7234	$5.72	$5.70	$5.70
Purchase #6	$211.32	10.404%	$233.3057	$233.31	$233.30	$233.30
Purchase #7	$78.43	5.618%	$82.8362	$82.84	$82.85	$82.80
7 purchase totals =	$697.60		$760.5114	$760.51	$760.45	$760.40