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	$238.74	9.539%	$261.5134	$261.51	$261.50	$261.50
Purchase #2	$164.85	12.558%	$185.5519	$185.55	$185.55	$185.60
Purchase #3	$143.31	3.247%	$147.9633	$147.96	$147.95	$148.00
Purchase #4	$90.29	10.519%	$99.7876	$99.79	$99.80	$99.80
Purchase #5	$32.36	10.589%	$35.7866	$35.79	$35.80	$35.80
Purchase #6	$20.61	5.400%	$21.7229	$21.72	$21.70	$21.70
Purchase #7	$238.34	8.681%	$259.0303	$259.03	$259.05	$259.00
7 purchase totals =	$928.50		$1,011.3560	$1,011.35	$1,011.35	$1,011.40