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	$150.84	10.685%	$166.9573	$166.96	$166.95	$167.00
Purchase #2	$32.79	9.300%	$35.8395	$35.84	$35.85	$35.80
Purchase #3	$58.35	5.339%	$61.4653	$61.47	$61.45	$61.50
Purchase #4	$85.50	8.808%	$93.0308	$93.03	$93.05	$93.00
Purchase #5	$109.50	12.458%	$123.1415	$123.14	$123.15	$123.10
Purchase #6	$98.75	6.630%	$105.2971	$105.30	$105.30	$105.30
Purchase #7	$218.61	12.308%	$245.5165	$245.52	$245.50	$245.50
7 purchase totals =	$754.34		$831.2480	$831.26	$831.25	$831.20