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	$94.85	9.172%	$103.5496	$103.55	$103.55	$103.50
Purchase #2	$178.28	10.132%	$196.3433	$196.34	$196.35	$196.30
Purchase #3	$87.38	5.171%	$91.8984	$91.90	$91.90	$91.90
Purchase #4	$12.41	3.807%	$12.8824	$12.88	$12.90	$12.90
Purchase #5	$161.63	5.224%	$170.0736	$170.07	$170.05	$170.10
Purchase #6	$212.69	11.759%	$237.7002	$237.70	$237.70	$237.70
Purchase #7	$7.38	5.749%	$7.8043	$7.80	$7.80	$7.80
7 purchase totals =	$754.62		$820.2518	$820.24	$820.25	$820.20