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	$40.47	11.244%	$45.0204	$45.02	$45.00	$45.00
Purchase #2	$209.50	4.294%	$218.4959	$218.50	$218.50	$218.50
Purchase #3	$222.70	7.799%	$240.0684	$240.07	$240.05	$240.10
Purchase #4	$82.95	9.146%	$90.5366	$90.54	$90.55	$90.50
Purchase #5	$185.45	11.698%	$207.1439	$207.14	$207.15	$207.10
Purchase #6	$147.35	3.861%	$153.0392	$153.04	$153.05	$153.00
Purchase #7	$214.71	3.502%	$222.2291	$222.23	$222.25	$222.20
7 purchase totals =	$1,103.13		$1,176.5335	$1,176.54	$1,176.55	$1,176.40