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	$176.25	13.315%	$199.7177	$199.72	$199.70	$199.70
Purchase #2	$138.50	3.659%	$143.5677	$143.57	$143.55	$143.60
Purchase #3	$39.85	11.229%	$44.3248	$44.32	$44.30	$44.30
Purchase #4	$55.76	6.102%	$59.1625	$59.16	$59.15	$59.20
Purchase #5	$152.92	11.831%	$171.012	$171.01	$171.00	$171.00
Purchase #6	$29.75	10.347%	$32.8282	$32.83	$32.85	$32.80
Purchase #7	$97.27	12.197%	$109.134	$109.13	$109.15	$109.10
7 purchase totals =	$690.30		$759.7469	$759.74	$759.70	$759.70