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	$61.80	9.849%	$67.8867	$67.89	$67.90	$67.90
Purchase #2	$245.58	3.477%	$254.1188	$254.12	$254.10	$254.10
Purchase #3	$59.92	3.593%	$62.0729	$62.07	$62.05	$62.10
Purchase #4	$219.83	3.758%	$228.0912	$228.09	$228.10	$228.10
Purchase #5	$177.32	13.261%	$200.8344	$200.83	$200.85	$200.80
Purchase #6	$151.29	12.320%	$169.9289	$169.93	$169.95	$169.90
Purchase #7	$249.61	3.790%	$259.0702	$259.07	$259.05	$259.10
7 purchase totals =	$1,165.35		$1,242.0031	$1,242.00	$1,242.00	$1,242.00