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	$161.69	11.547%	$180.3603	$180.36	$180.35	$180.40
Purchase #2	$235.88	8.273%	$255.3944	$255.39	$255.40	$255.40
Purchase #3	$72.68	13.614%	$82.5747	$82.57	$82.55	$82.60
Purchase #4	$85.51	5.815%	$90.4824	$90.48	$90.50	$90.50
Purchase #5	$112.95	5.560%	$119.23	$119.23	$119.25	$119.20
Purchase #6	$55.71	5.232%	$58.6247	$58.62	$58.60	$58.60
Purchase #7	$89.63	10.428%	$98.9766	$98.98	$99.00	$99.00
7 purchase totals =	$814.05		$885.6431	$885.63	$885.65	$885.70