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	$13.91	3.518%	$14.3994	$14.40	$14.40	$14.40
Purchase #2	$181.74	7.244%	$194.9052	$194.91	$194.90	$194.90
Purchase #3	$13.77	13.356%	$15.6091	$15.61	$15.60	$15.60
Purchase #4	$239.59	3.424%	$247.7936	$247.79	$247.80	$247.80
Purchase #5	$93.74	12.655%	$105.6028	$105.60	$105.60	$105.60
Purchase #6	$169.89	11.552%	$189.5157	$189.52	$189.50	$189.50
Purchase #7	$183.87	6.813%	$196.3971	$196.40	$196.40	$196.40
7 purchase totals =	$896.51		$964.2229	$964.23	$964.20	$964.20