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	$96.77	5.153%	$101.7566	$101.76	$101.75	$101.80
Purchase #2	$37.57	9.286%	$41.0588	$41.06	$41.05	$41.10
Purchase #3	$129.36	9.628%	$141.8148	$141.81	$141.80	$141.80
Purchase #4	$66.96	7.128%	$71.7329	$71.73	$71.75	$71.70
Purchase #5	$204.57	3.564%	$211.8609	$211.86	$211.85	$211.90
Purchase #6	$127.84	13.338%	$144.8913	$144.89	$144.90	$144.90
Purchase #7	$147.90	13.444%	$167.7837	$167.78	$167.80	$167.80
7 purchase totals =	$810.97		$880.8990	$880.89	$880.90	$881.00