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	$206.96	7.811%	$223.1256	$223.13	$223.15	$223.10
Purchase #2	$19.29	11.294%	$21.4686	$21.47	$21.45	$21.50
Purchase #3	$47.31	13.540%	$53.7158	$53.72	$53.70	$53.70
Purchase #4	$228.49	11.481%	$254.7229	$254.72	$254.70	$254.70
Purchase #5	$43.29	9.864%	$47.5601	$47.56	$47.55	$47.60
Purchase #6	$188.64	8.774%	$205.1913	$205.19	$205.20	$205.20
Purchase #7	$240.61	6.410%	$256.0331	$256.03	$256.05	$256.00
7 purchase totals =	$974.59		$1,061.8174	$1,061.82	$1,061.80	$1,061.80