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	$178.63	5.166%	$187.858	$187.86	$187.85	$187.90
Purchase #2	$10.71	12.272%	$12.0243	$12.02	$12.00	$12.00
Purchase #3	$220.40	7.342%	$236.5818	$236.58	$236.60	$236.60
Purchase #4	$166.46	12.563%	$187.3724	$187.37	$187.35	$187.40
Purchase #5	$218.56	11.358%	$243.384	$243.38	$243.40	$243.40
Purchase #6	$42.71	11.841%	$47.7673	$47.77	$47.75	$47.80
Purchase #7	$133.46	4.766%	$139.8207	$139.82	$139.80	$139.80
7 purchase totals =	$970.93		$1,054.8085	$1,054.80	$1,054.75	$1,054.90