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	$24.29	6.869%	$25.9585	$25.96	$25.95	$26.00
Purchase #2	$240.40	13.502%	$272.8588	$272.86	$272.85	$272.90
Purchase #3	$127.92	8.747%	$139.1092	$139.11	$139.10	$139.10
Purchase #4	$128.56	8.545%	$139.5455	$139.55	$139.55	$139.50
Purchase #5	$123.88	4.118%	$128.9814	$128.98	$129.00	$129.00
Purchase #6	$170.27	7.138%	$182.4239	$182.42	$182.40	$182.40
Purchase #7	$77.56	11.816%	$86.7245	$86.72	$86.70	$86.70
7 purchase totals =	$892.88		$975.6018	$975.60	$975.55	$975.60