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	$146.77	8.258%	$158.8903	$158.89	$158.90	$158.90
Purchase #2	$109.80	13.781%	$124.9315	$124.93	$124.95	$124.90
Purchase #3	$104.28	5.851%	$110.3814	$110.38	$110.40	$110.40
Purchase #4	$199.65	5.248%	$210.1276	$210.13	$210.15	$210.10
Purchase #5	$180.77	6.585%	$192.6737	$192.67	$192.65	$192.70
Purchase #6	$125.35	6.581%	$133.5993	$133.60	$133.60	$133.60
Purchase #7	$96.27	4.473%	$100.5762	$100.58	$100.60	$100.60
7 purchase totals =	$962.89		$1,031.1800	$1,031.18	$1,031.25	$1,031.20