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	$132.66	6.698%	$141.5456	$141.55	$141.55	$141.50
Purchase #2	$33.72	4.721%	$35.3119	$35.31	$35.30	$35.30
Purchase #3	$139.96	7.429%	$150.3576	$150.36	$150.35	$150.40
Purchase #4	$174.64	3.725%	$181.1453	$181.15	$181.15	$181.10
Purchase #5	$92.49	13.586%	$105.0557	$105.06	$105.05	$105.10
Purchase #6	$241.90	7.862%	$260.9182	$260.92	$260.90	$260.90
Purchase #7	$65.31	9.199%	$71.3179	$71.32	$71.30	$71.30
7 purchase totals =	$880.68		$945.6522	$945.67	$945.60	$945.60