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	$209.51	10.655%	$231.8333	$231.83	$231.85	$231.80
Purchase #2	$154.31	12.507%	$173.6096	$173.61	$173.60	$173.60
Purchase #3	$25.61	7.634%	$27.5651	$27.57	$27.55	$27.60
Purchase #4	$6.80	11.418%	$7.5764	$7.58	$7.60	$7.60
Purchase #5	$148.88	12.582%	$167.6121	$167.61	$167.60	$167.60
Purchase #6	$202.83	11.370%	$225.8918	$225.89	$225.90	$225.90
Purchase #7	$220.54	10.119%	$242.8564	$242.86	$242.85	$242.90
7 purchase totals =	$968.48		$1,076.9447	$1,076.95	$1,076.95	$1,077.00