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	$211.67	13.411%	$240.0571	$240.06	$240.05	$240.10
Purchase #2	$187.99	6.836%	$200.841	$200.84	$200.85	$200.80
Purchase #3	$143.70	4.848%	$150.6666	$150.67	$150.65	$150.70
Purchase #4	$29.48	8.116%	$31.8726	$31.87	$31.85	$31.90
Purchase #5	$159.31	3.138%	$164.3091	$164.31	$164.30	$164.30
Purchase #6	$240.48	6.140%	$255.2455	$255.25	$255.25	$255.20
Purchase #7	$212.67	4.164%	$221.5256	$221.53	$221.55	$221.50
7 purchase totals =	$1,185.30		$1,264.5175	$1,264.53	$1,264.50	$1,264.50