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	$13.68	3.416%	$14.1473	$14.15	$14.15	$14.10
Purchase #2	$247.59	13.164%	$280.1827	$280.18	$280.20	$280.20
Purchase #3	$85.44	4.738%	$89.4881	$89.49	$89.50	$89.50
Purchase #4	$69.98	4.131%	$72.8709	$72.87	$72.85	$72.90
Purchase #5	$85.88	11.617%	$95.8567	$95.86	$95.85	$95.90
Purchase #6	$32.38	6.130%	$34.3649	$34.36	$34.35	$34.40
Purchase #7	$250.92	8.211%	$271.523	$271.52	$271.50	$271.50
7 purchase totals =	$785.87		$858.4336	$858.43	$858.40	$858.50