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	$249.45	6.580%	$265.8638	$265.86	$265.85	$265.90
Purchase #2	$12.49	6.626%	$13.3176	$13.32	$13.30	$13.30
Purchase #3	$160.72	5.353%	$169.3233	$169.32	$169.30	$169.30
Purchase #4	$85.27	5.290%	$89.7808	$89.78	$89.80	$89.80
Purchase #5	$92.86	12.184%	$104.1741	$104.17	$104.15	$104.20
Purchase #6	$169.54	7.544%	$182.3301	$182.33	$182.35	$182.30
Purchase #7	$106.38	5.722%	$112.4671	$112.47	$112.45	$112.50
7 purchase totals =	$876.71		$937.2568	$937.25	$937.20	$937.30