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	$23.26	11.108%	$25.8437	$25.84	$25.85	$25.80
Purchase #2	$11.85	11.150%	$13.1713	$13.17	$13.15	$13.20
Purchase #3	$123.25	12.821%	$139.0519	$139.05	$139.05	$139.10
Purchase #4	$222.26	6.573%	$236.8691	$236.87	$236.85	$236.90
Purchase #5	$236.61	3.611%	$245.154	$245.15	$245.15	$245.20
Purchase #6	$210.56	6.152%	$223.5137	$223.51	$223.50	$223.50
Purchase #7	$148.40	6.636%	$158.2478	$158.25	$158.25	$158.20
7 purchase totals =	$976.19		$1,041.8515	$1,041.84	$1,041.80	$1,041.90