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	$225.86	13.171%	$255.608	$255.61	$255.60	$255.60
Purchase #2	$42.65	5.782%	$45.116	$45.12	$45.10	$45.10
Purchase #3	$20.34	5.112%	$21.3798	$21.38	$21.40	$21.40
Purchase #4	$161.85	4.839%	$169.6819	$169.68	$169.70	$169.70
Purchase #5	$139.76	11.869%	$156.3481	$156.35	$156.35	$156.30
Purchase #6	$153.75	5.684%	$162.4892	$162.49	$162.50	$162.50
Purchase #7	$55.44	6.656%	$59.1301	$59.13	$59.15	$59.10
7 purchase totals =	$799.65		$869.7531	$869.76	$869.80	$869.70