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	$162.54	6.582%	$173.2384	$173.24	$173.25	$173.20
Purchase #2	$48.67	6.540%	$51.853	$51.85	$51.85	$51.90
Purchase #3	$162.41	3.712%	$168.4387	$168.44	$168.45	$168.40
Purchase #4	$111.82	5.601%	$118.083	$118.08	$118.10	$118.10
Purchase #5	$143.61	10.315%	$158.4234	$158.42	$158.40	$158.40
Purchase #6	$206.61	8.233%	$223.6202	$223.62	$223.60	$223.60
Purchase #7	$219.61	8.465%	$238.2	$238.20	$238.20	$238.20
7 purchase totals =	$1,055.27		$1,131.8567	$1,131.85	$1,131.85	$1,131.80