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	$111.34	12.392%	$125.1373	$125.14	$125.15	$125.10
Purchase #2	$110.39	6.445%	$117.5046	$117.50	$117.50	$117.50
Purchase #3	$78.48	12.799%	$88.5247	$88.52	$88.50	$88.50
Purchase #4	$197.79	12.697%	$222.9034	$222.90	$222.90	$222.90
Purchase #5	$39.29	7.378%	$42.1888	$42.19	$42.20	$42.20
Purchase #6	$228.89	11.658%	$255.574	$255.57	$255.55	$255.60
Purchase #7	$17.88	9.509%	$19.5802	$19.58	$19.60	$19.60
7 purchase totals =	$784.06		$871.4130	$871.40	$871.40	$871.40