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	$34.48	10.378%	$38.0583	$38.06	$38.05	$38.10
Purchase #2	$90.27	9.145%	$98.5252	$98.53	$98.55	$98.50
Purchase #3	$213.28	8.732%	$231.9036	$231.90	$231.90	$231.90
Purchase #4	$225.61	13.198%	$255.386	$255.39	$255.40	$255.40
Purchase #5	$160.28	5.398%	$168.9319	$168.93	$168.95	$168.90
Purchase #6	$229.91	5.417%	$242.3642	$242.36	$242.35	$242.40
Purchase #7	$27.25	13.854%	$31.0252	$31.03	$31.05	$31.00
7 purchase totals =	$981.08		$1,066.1944	$1,066.20	$1,066.25	$1,066.20