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	$126.26	9.457%	$138.2004	$138.20	$138.20	$138.20
Purchase #2	$47.77	9.608%	$52.3597	$52.36	$52.35	$52.40
Purchase #3	$12.84	7.371%	$13.7864	$13.79	$13.80	$13.80
Purchase #4	$72.90	7.457%	$78.3362	$78.34	$78.35	$78.30
Purchase #5	$150.31	10.365%	$165.8896	$165.89	$165.90	$165.90
Purchase #6	$158.87	5.454%	$167.5348	$167.53	$167.55	$167.50
Purchase #7	$184.57	5.400%	$194.5368	$194.54	$194.55	$194.50
7 purchase totals =	$753.52		$810.6439	$810.65	$810.70	$810.60