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	$234.76	4.691%	$245.7726	$245.77	$245.75	$245.80
Purchase #2	$198.78	11.790%	$222.2162	$222.22	$222.20	$222.20
Purchase #3	$119.43	3.790%	$123.9564	$123.96	$123.95	$124.00
Purchase #4	$125.48	7.418%	$134.7881	$134.79	$134.80	$134.80
Purchase #5	$164.32	12.843%	$185.4236	$185.42	$185.40	$185.40
Purchase #6	$144.69	9.570%	$158.5368	$158.54	$158.55	$158.50
Purchase #7	$112.28	12.145%	$125.9164	$125.92	$125.90	$125.90
7 purchase totals =	$1,099.74		$1,196.6101	$1,196.62	$1,196.55	$1,196.60