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	$8.32	10.356%	$9.1816	$9.18	$9.20	$9.20
Purchase #2	$14.26	6.140%	$15.1356	$15.14	$15.15	$15.10
Purchase #3	$171.85	10.150%	$189.2928	$189.29	$189.30	$189.30
Purchase #4	$53.71	10.103%	$59.1363	$59.14	$59.15	$59.10
Purchase #5	$64.50	8.417%	$69.929	$69.93	$69.95	$69.90
Purchase #6	$79.34	7.807%	$85.5341	$85.53	$85.55	$85.50
Purchase #7	$56.67	4.248%	$59.0773	$59.08	$59.10	$59.10
7 purchase totals =	$448.65		$487.2867	$487.29	$487.40	$487.20