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	$86.53	6.627%	$92.2643	$92.26	$92.25	$92.30
Purchase #2	$105.93	12.579%	$119.2549	$119.25	$119.25	$119.30
Purchase #3	$194.48	9.453%	$212.8642	$212.86	$212.85	$212.90
Purchase #4	$182.94	6.801%	$195.3817	$195.38	$195.40	$195.40
Purchase #5	$90.36	9.718%	$99.1412	$99.14	$99.15	$99.10
Purchase #6	$96.78	8.646%	$105.1476	$105.15	$105.15	$105.10
Purchase #7	$237.60	8.302%	$257.3256	$257.33	$257.35	$257.30
7 purchase totals =	$994.62		$1,081.3795	$1,081.37	$1,081.40	$1,081.40