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	$120.43	10.323%	$132.862	$132.86	$132.85	$132.90
Purchase #2	$120.48	5.796%	$127.463	$127.46	$127.45	$127.50
Purchase #3	$239.96	7.568%	$258.1202	$258.12	$258.10	$258.10
Purchase #4	$35.77	12.854%	$40.3679	$40.37	$40.35	$40.40
Purchase #5	$149.42	10.351%	$164.8865	$164.89	$164.90	$164.90
Purchase #6	$190.69	13.821%	$217.0453	$217.05	$217.05	$217.00
Purchase #7	$78.57	4.751%	$82.3029	$82.30	$82.30	$82.30
7 purchase totals =	$935.32		$1,023.0478	$1,023.05	$1,023.00	$1,023.10