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	$141.97	13.763%	$161.5093	$161.51	$161.50	$161.50
Purchase #2	$176.89	7.424%	$190.0223	$190.02	$190.00	$190.00
Purchase #3	$57.63	3.442%	$59.6136	$59.61	$59.60	$59.60
Purchase #4	$75.60	12.452%	$85.0137	$85.01	$85.00	$85.00
Purchase #5	$184.59	4.356%	$192.6307	$192.63	$192.65	$192.60
Purchase #6	$115.94	10.421%	$128.0221	$128.02	$128.00	$128.00
Purchase #7	$211.28	11.156%	$234.8504	$234.85	$234.85	$234.90
7 purchase totals =	$963.90		$1,051.6621	$1,051.65	$1,051.60	$1,051.60