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	$64.52	4.322%	$67.3086	$67.31	$67.30	$67.30
Purchase #2	$122.59	4.831%	$128.5123	$128.51	$128.50	$128.50
Purchase #3	$197.45	12.868%	$222.8579	$222.86	$222.85	$222.90
Purchase #4	$180.32	5.652%	$190.5117	$190.51	$190.50	$190.50
Purchase #5	$237.85	10.349%	$262.4651	$262.47	$262.45	$262.50
Purchase #6	$162.98	4.850%	$170.8845	$170.88	$170.90	$170.90
Purchase #7	$87.86	5.157%	$92.3909	$92.39	$92.40	$92.40
7 purchase totals =	$1,053.57		$1,134.9310	$1,134.93	$1,134.90	$1,135.00