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	$64.38	5.412%	$67.8642	$67.86	$67.85	$67.90
Purchase #2	$218.62	9.656%	$239.7299	$239.73	$239.75	$239.70
Purchase #3	$64.91	12.236%	$72.8524	$72.85	$72.85	$72.90
Purchase #4	$199.86	5.830%	$211.5118	$211.51	$211.50	$211.50
Purchase #5	$161.52	12.141%	$181.1301	$181.13	$181.15	$181.10
Purchase #6	$141.61	11.586%	$158.0169	$158.02	$158.00	$158.00
Purchase #7	$81.38	8.709%	$88.4674	$88.47	$88.45	$88.50
7 purchase totals =	$932.28		$1,019.5727	$1,019.57	$1,019.55	$1,019.60