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	$198.28	10.700%	$219.496	$219.50	$219.50	$219.50
Purchase #2	$202.92	9.785%	$222.7757	$222.78	$222.80	$222.80
Purchase #3	$189.89	3.426%	$196.3956	$196.40	$196.40	$196.40
Purchase #4	$212.35	4.656%	$222.237	$222.24	$222.25	$222.20
Purchase #5	$78.65	9.167%	$85.8598	$85.86	$85.85	$85.90
Purchase #6	$214.28	11.767%	$239.4943	$239.49	$239.50	$239.50
Purchase #7	$100.63	11.508%	$112.2105	$112.21	$112.20	$112.20
7 purchase totals =	$1,197.00		$1,298.4689	$1,298.48	$1,298.50	$1,298.50