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	$91.90	6.290%	$97.6805	$97.68	$97.70	$97.70
Purchase #2	$186.93	8.650%	$203.0994	$203.10	$203.10	$203.10
Purchase #3	$114.47	7.331%	$122.8618	$122.86	$122.85	$122.90
Purchase #4	$30.36	4.127%	$31.613	$31.61	$31.60	$31.60
Purchase #5	$163.42	10.622%	$180.7785	$180.78	$180.80	$180.80
Purchase #6	$81.72	11.187%	$90.862	$90.86	$90.85	$90.90
Purchase #7	$56.88	4.114%	$59.22	$59.22	$59.20	$59.20
7 purchase totals =	$725.68		$786.1152	$786.11	$786.10	$786.20