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	$201.64	3.735%	$209.1713	$209.17	$209.15	$209.20
Purchase #2	$62.67	4.477%	$65.4757	$65.48	$65.50	$65.50
Purchase #3	$95.61	9.230%	$104.4348	$104.43	$104.45	$104.40
Purchase #4	$98.55	10.858%	$109.2506	$109.25	$109.25	$109.30
Purchase #5	$56.61	11.501%	$63.1207	$63.12	$63.10	$63.10
Purchase #6	$102.92	6.582%	$109.6942	$109.69	$109.70	$109.70
Purchase #7	$168.69	12.604%	$189.9517	$189.95	$189.95	$190.00
7 purchase totals =	$786.69		$851.0990	$851.09	$851.10	$851.20