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	$83.95	13.458%	$95.248	$95.25	$95.25	$95.20
Purchase #2	$173.72	6.721%	$185.3957	$185.40	$185.40	$185.40
Purchase #3	$142.28	12.870%	$160.5914	$160.59	$160.60	$160.60
Purchase #4	$226.63	7.404%	$243.4097	$243.41	$243.40	$243.40
Purchase #5	$192.70	12.535%	$216.8549	$216.85	$216.85	$216.90
Purchase #6	$140.31	7.187%	$150.3941	$150.39	$150.40	$150.40
Purchase #7	$239.81	9.704%	$263.0812	$263.08	$263.10	$263.10
7 purchase totals =	$1,199.40		$1,314.9750	$1,314.97	$1,315.00	$1,315.00