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	$145.62	4.545%	$152.2384	$152.24	$152.25	$152.20
Purchase #2	$223.96	7.200%	$240.0851	$240.09	$240.10	$240.10
Purchase #3	$143.64	10.325%	$158.4708	$158.47	$158.45	$158.50
Purchase #4	$89.93	6.844%	$96.0848	$96.08	$96.10	$96.10
Purchase #5	$13.46	11.702%	$15.0351	$15.04	$15.05	$15.00
Purchase #6	$161.47	3.721%	$167.4783	$167.48	$167.50	$167.50
Purchase #7	$36.32	3.246%	$37.4989	$37.50	$37.50	$37.50
7 purchase totals =	$814.40		$866.8914	$866.90	$866.95	$866.90