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	$191.60	12.744%	$216.0175	$216.02	$216.00	$216.00
Purchase #2	$184.60	10.816%	$204.5663	$204.57	$204.55	$204.60
Purchase #3	$169.30	10.530%	$187.1273	$187.13	$187.15	$187.10
Purchase #4	$85.71	5.463%	$90.3923	$90.39	$90.40	$90.40
Purchase #5	$132.79	11.409%	$147.94	$147.94	$147.95	$147.90
Purchase #6	$180.60	10.755%	$200.0235	$200.02	$200.00	$200.00
Purchase #7	$87.81	12.782%	$99.0339	$99.03	$99.05	$99.00
7 purchase totals =	$1,032.41		$1,145.1008	$1,145.10	$1,145.10	$1,145.00