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	$177.30	10.662%	$196.2037	$196.20	$196.20	$196.20
Purchase #2	$210.85	6.149%	$223.8152	$223.82	$223.80	$223.80
Purchase #3	$81.73	13.186%	$92.5069	$92.51	$92.50	$92.50
Purchase #4	$65.67	8.225%	$71.0714	$71.07	$71.05	$71.10
Purchase #5	$78.73	8.369%	$85.3189	$85.32	$85.30	$85.30
Purchase #6	$164.82	10.539%	$182.1904	$182.19	$182.20	$182.20
Purchase #7	$142.82	13.377%	$161.925	$161.93	$161.95	$161.90
7 purchase totals =	$921.92		$1,013.0315	$1,013.04	$1,013.00	$1,013.00