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	$118.40	4.609%	$123.8571	$123.86	$123.85	$123.90
Purchase #2	$236.54	9.430%	$258.8457	$258.85	$258.85	$258.80
Purchase #3	$198.60	12.709%	$223.8401	$223.84	$223.85	$223.80
Purchase #4	$24.90	5.651%	$26.3071	$26.31	$26.30	$26.30
Purchase #5	$55.53	3.366%	$57.3991	$57.40	$57.40	$57.40
Purchase #6	$240.85	5.425%	$253.9161	$253.92	$253.90	$253.90
Purchase #7	$92.53	3.382%	$95.6594	$95.66	$95.65	$95.70
7 purchase totals =	$967.35		$1,039.8246	$1,039.84	$1,039.80	$1,039.80