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	$104.80	4.179%	$109.1796	$109.18	$109.20	$109.20
Purchase #2	$174.75	12.568%	$196.7126	$196.71	$196.70	$196.70
Purchase #3	$249.69	5.711%	$263.9498	$263.95	$263.95	$263.90
Purchase #4	$90.53	12.546%	$101.8879	$101.89	$101.90	$101.90
Purchase #5	$69.52	8.505%	$75.4327	$75.43	$75.45	$75.40
Purchase #6	$18.83	8.659%	$20.4605	$20.46	$20.45	$20.50
Purchase #7	$232.56	11.338%	$258.9277	$258.93	$258.95	$258.90
7 purchase totals =	$940.68		$1,026.5508	$1,026.55	$1,026.60	$1,026.50