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	$236.76	11.447%	$263.8619	$263.86	$263.85	$263.90
Purchase #2	$96.73	7.658%	$104.1376	$104.14	$104.15	$104.10
Purchase #3	$8.61	10.306%	$9.4973	$9.50	$9.50	$9.50
Purchase #4	$136.35	11.766%	$152.3929	$152.39	$152.40	$152.40
Purchase #5	$206.94	7.857%	$223.1993	$223.20	$223.20	$223.20
Purchase #6	$48.45	9.107%	$52.8623	$52.86	$52.85	$52.90
Purchase #7	$201.88	11.723%	$225.5464	$225.55	$225.55	$225.50
7 purchase totals =	$935.72		$1,031.4977	$1,031.50	$1,031.50	$1,031.50