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	$179.32	9.803%	$196.8987	$196.90	$196.90	$196.90
Purchase #2	$82.41	8.300%	$89.25	$89.25	$89.25	$89.30
Purchase #3	$61.37	6.717%	$65.4922	$65.49	$65.50	$65.50
Purchase #4	$7.69	4.808%	$8.0597	$8.06	$8.05	$8.10
Purchase #5	$123.47	4.255%	$128.7236	$128.72	$128.70	$128.70
Purchase #6	$9.84	10.470%	$10.8702	$10.87	$10.85	$10.90
Purchase #7	$180.44	11.797%	$201.7265	$201.73	$201.75	$201.70
7 purchase totals =	$644.54		$701.0209	$701.02	$701.00	$701.10