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	$180.83	10.560%	$199.9256	$199.93	$199.95	$199.90
Purchase #2	$78.46	9.418%	$85.8494	$85.85	$85.85	$85.80
Purchase #3	$109.65	8.419%	$118.8814	$118.88	$118.90	$118.90
Purchase #4	$130.65	6.458%	$139.0874	$139.09	$139.10	$139.10
Purchase #5	$152.95	7.535%	$164.4748	$164.47	$164.45	$164.50
Purchase #6	$120.31	7.152%	$128.9146	$128.91	$128.90	$128.90
Purchase #7	$78.26	11.171%	$87.0024	$87.00	$87.00	$87.00
7 purchase totals =	$851.11		$924.1356	$924.13	$924.15	$924.10