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	$109.69	7.586%	$118.0111	$118.01	$118.00	$118.00
Purchase #2	$86.95	7.408%	$93.3913	$93.39	$93.40	$93.40
Purchase #3	$66.57	12.338%	$74.7834	$74.78	$74.80	$74.80
Purchase #4	$158.48	4.661%	$165.8668	$165.87	$165.85	$165.90
Purchase #5	$203.86	8.339%	$220.8599	$220.86	$220.85	$220.90
Purchase #6	$228.72	12.114%	$256.4271	$256.43	$256.45	$256.40
Purchase #7	$162.26	10.730%	$179.6705	$179.67	$179.65	$179.70
7 purchase totals =	$1,016.53		$1,109.0101	$1,109.01	$1,109.00	$1,109.10