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	$14.67	5.818%	$15.5235	$15.52	$15.50	$15.50
Purchase #2	$114.98	9.538%	$125.9468	$125.95	$125.95	$125.90
Purchase #3	$168.78	10.146%	$185.9044	$185.90	$185.90	$185.90
Purchase #4	$58.43	5.646%	$61.729	$61.73	$61.75	$61.70
Purchase #5	$99.59	13.832%	$113.3653	$113.37	$113.35	$113.40
Purchase #6	$240.85	7.697%	$259.3882	$259.39	$259.40	$259.40
Purchase #7	$57.31	4.583%	$59.9365	$59.94	$59.95	$59.90
7 purchase totals =	$754.61		$821.7937	$821.80	$821.80	$821.70