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	$56.37	4.565%	$58.9433	$58.94	$58.95	$58.90
Purchase #2	$56.48	4.429%	$58.9815	$58.98	$59.00	$59.00
Purchase #3	$71.28	9.779%	$78.2505	$78.25	$78.25	$78.30
Purchase #4	$33.74	5.260%	$35.5147	$35.51	$35.50	$35.50
Purchase #5	$110.31	8.275%	$119.4382	$119.44	$119.45	$119.40
Purchase #6	$32.51	5.339%	$34.2457	$34.25	$34.25	$34.20
Purchase #7	$100.92	5.305%	$106.2738	$106.27	$106.25	$106.30
7 purchase totals =	$461.61		$491.6477	$491.64	$491.65	$491.60