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	$201.41	7.158%	$215.8269	$215.83	$215.85	$215.80
Purchase #2	$153.74	13.611%	$174.6656	$174.67	$174.65	$174.70
Purchase #3	$146.55	6.687%	$156.3498	$156.35	$156.35	$156.30
Purchase #4	$152.74	8.349%	$165.4923	$165.49	$165.50	$165.50
Purchase #5	$11.78	9.419%	$12.8896	$12.89	$12.90	$12.90
Purchase #6	$59.34	13.496%	$67.3485	$67.35	$67.35	$67.30
Purchase #7	$113.27	3.668%	$117.4247	$117.42	$117.40	$117.40
7 purchase totals =	$838.83		$909.9974	$910.00	$910.00	$909.90