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	$189.66	4.408%	$198.0202	$198.02	$198.00	$198.00
Purchase #2	$50.77	4.227%	$52.916	$52.92	$52.90	$52.90
Purchase #3	$240.63	3.646%	$249.4034	$249.40	$249.40	$249.40
Purchase #4	$130.71	9.779%	$143.4921	$143.49	$143.50	$143.50
Purchase #5	$9.46	11.217%	$10.5211	$10.52	$10.50	$10.50
Purchase #6	$50.86	9.329%	$55.6047	$55.60	$55.60	$55.60
Purchase #7	$103.48	11.141%	$115.0087	$115.01	$115.00	$115.00
7 purchase totals =	$775.57		$824.9662	$824.96	$824.90	$824.90