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	$118.68	9.860%	$130.3818	$130.38	$130.40	$130.40
Purchase #2	$90.88	4.668%	$95.1223	$95.12	$95.10	$95.10
Purchase #3	$230.36	12.643%	$259.4844	$259.48	$259.50	$259.50
Purchase #4	$190.43	10.130%	$209.7206	$209.72	$209.70	$209.70
Purchase #5	$203.68	12.566%	$229.2744	$229.27	$229.25	$229.30
Purchase #6	$200.78	11.512%	$223.8938	$223.89	$223.90	$223.90
Purchase #7	$139.35	10.522%	$154.0124	$154.01	$154.00	$154.00
7 purchase totals =	$1,174.16		$1,301.8897	$1,301.87	$1,301.85	$1,301.90