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	$90.48	13.585%	$102.7717	$102.77	$102.75	$102.80
Purchase #2	$188.36	13.728%	$214.2181	$214.22	$214.20	$214.20
Purchase #3	$246.30	13.123%	$278.6219	$278.62	$278.60	$278.60
Purchase #4	$225.58	13.816%	$256.7461	$256.75	$256.75	$256.70
Purchase #5	$121.57	13.483%	$137.9613	$137.96	$137.95	$138.00
Purchase #6	$135.33	12.758%	$152.5954	$152.60	$152.60	$152.60
Purchase #7	$38.81	9.644%	$42.5528	$42.55	$42.55	$42.60
7 purchase totals =	$1,046.43		$1,185.4673	$1,185.47	$1,185.40	$1,185.50