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	$203.61	9.326%	$222.5987	$222.60	$222.60	$222.60
Purchase #2	$189.79	10.206%	$209.16	$209.16	$209.15	$209.20
Purchase #3	$135.73	3.217%	$140.0964	$140.10	$140.10	$140.10
Purchase #4	$94.41	9.621%	$103.4932	$103.49	$103.50	$103.50
Purchase #5	$40.75	9.536%	$44.6359	$44.64	$44.65	$44.60
Purchase #6	$111.46	12.347%	$125.222	$125.22	$125.20	$125.20
Purchase #7	$156.55	10.385%	$172.8077	$172.81	$172.80	$172.80
7 purchase totals =	$932.30		$1,018.0139	$1,018.02	$1,018.00	$1,018.00