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	$65.54	8.394%	$71.0414	$71.04	$71.05	$71.00
Purchase #2	$204.29	7.166%	$218.9294	$218.93	$218.95	$218.90
Purchase #3	$45.89	4.418%	$47.9174	$47.92	$47.90	$47.90
Purchase #4	$185.78	10.421%	$205.1401	$205.14	$205.15	$205.10
Purchase #5	$157.43	8.840%	$171.3468	$171.35	$171.35	$171.30
Purchase #6	$86.26	4.830%	$90.4264	$90.43	$90.45	$90.40
Purchase #7	$50.94	9.323%	$55.6891	$55.69	$55.70	$55.70
7 purchase totals =	$796.13		$860.4906	$860.50	$860.55	$860.30