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	$56.60	11.871%	$63.319	$63.32	$63.30	$63.30
Purchase #2	$40.36	12.119%	$45.2512	$45.25	$45.25	$45.30
Purchase #3	$64.79	12.275%	$72.743	$72.74	$72.75	$72.70
Purchase #4	$212.88	6.803%	$227.3622	$227.36	$227.35	$227.40
Purchase #5	$35.90	5.638%	$37.924	$37.92	$37.90	$37.90
Purchase #6	$70.26	11.146%	$78.0912	$78.09	$78.10	$78.10
Purchase #7	$16.93	11.184%	$18.8235	$18.82	$18.80	$18.80
7 purchase totals =	$497.72		$543.5141	$543.50	$543.45	$543.50