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	$223.39	7.454%	$240.0415	$240.04	$240.05	$240.00
Purchase #2	$71.49	9.767%	$78.4724	$78.47	$78.45	$78.50
Purchase #3	$17.45	3.318%	$18.029	$18.03	$18.05	$18.00
Purchase #4	$123.31	13.766%	$140.2849	$140.28	$140.30	$140.30
Purchase #5	$216.99	12.447%	$243.9987	$244.00	$244.00	$244.00
Purchase #6	$240.57	9.376%	$263.1258	$263.13	$263.15	$263.10
Purchase #7	$35.45	8.843%	$38.5848	$38.58	$38.60	$38.60
7 purchase totals =	$928.65		$1,022.5371	$1,022.53	$1,022.60	$1,022.50