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	$215.89	9.542%	$236.4902	$236.49	$236.50	$236.50
Purchase #2	$230.85	4.337%	$240.862	$240.86	$240.85	$240.90
Purchase #3	$6.69	4.549%	$6.9943	$6.99	$7.00	$7.00
Purchase #4	$65.50	10.342%	$72.274	$72.27	$72.25	$72.30
Purchase #5	$103.33	6.404%	$109.9473	$109.95	$109.95	$109.90
Purchase #6	$62.87	12.780%	$70.9048	$70.90	$70.90	$70.90
Purchase #7	$59.72	11.295%	$66.4654	$66.47	$66.45	$66.50
7 purchase totals =	$744.85		$803.9380	$803.93	$803.90	$804.00