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	$114.70	11.631%	$128.0408	$128.04	$128.05	$128.00
Purchase #2	$148.26	5.284%	$156.0941	$156.09	$156.10	$156.10
Purchase #3	$102.48	10.285%	$113.0201	$113.02	$113.00	$113.00
Purchase #4	$154.77	10.638%	$171.2344	$171.23	$171.25	$171.20
Purchase #5	$80.80	13.636%	$91.8179	$91.82	$91.80	$91.80
Purchase #6	$222.31	8.222%	$240.5883	$240.59	$240.60	$240.60
Purchase #7	$180.64	6.621%	$192.6002	$192.60	$192.60	$192.60
7 purchase totals =	$1,003.96		$1,093.3958	$1,093.39	$1,093.40	$1,093.30