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	$242.46	10.152%	$267.0745	$267.07	$267.05	$267.10
Purchase #2	$191.76	7.445%	$206.0365	$206.04	$206.05	$206.00
Purchase #3	$153.71	9.654%	$168.5492	$168.55	$168.55	$168.50
Purchase #4	$76.77	6.180%	$81.5144	$81.51	$81.50	$81.50
Purchase #5	$134.87	9.400%	$147.5478	$147.55	$147.55	$147.50
Purchase #6	$90.43	13.248%	$102.4102	$102.41	$102.40	$102.40
Purchase #7	$128.89	7.132%	$138.0824	$138.08	$138.10	$138.10
7 purchase totals =	$1,018.89		$1,111.2150	$1,111.21	$1,111.20	$1,111.10