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	$35.26	5.646%	$37.2508	$37.25	$37.25	$37.30
Purchase #2	$82.31	3.699%	$85.3546	$85.35	$85.35	$85.40
Purchase #3	$151.44	9.854%	$166.3629	$166.36	$166.35	$166.40
Purchase #4	$41.36	11.824%	$46.2504	$46.25	$46.25	$46.30
Purchase #5	$232.29	11.682%	$259.4261	$259.43	$259.45	$259.40
Purchase #6	$216.89	12.359%	$243.6954	$243.70	$243.70	$243.70
Purchase #7	$178.38	7.420%	$191.6158	$191.62	$191.60	$191.60
7 purchase totals =	$937.93		$1,029.9560	$1,029.96	$1,029.95	$1,030.10