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	$145.90	7.540%	$156.9009	$156.90	$156.90	$156.90
Purchase #2	$219.68	4.461%	$229.4799	$229.48	$229.50	$229.50
Purchase #3	$78.56	12.403%	$88.3038	$88.30	$88.30	$88.30
Purchase #4	$101.90	11.133%	$113.2445	$113.24	$113.25	$113.20
Purchase #5	$213.56	3.757%	$221.5834	$221.58	$221.60	$221.60
Purchase #6	$108.52	4.751%	$113.6758	$113.68	$113.70	$113.70
Purchase #7	$127.85	3.504%	$132.3299	$132.33	$132.35	$132.30
7 purchase totals =	$995.97		$1,055.5182	$1,055.51	$1,055.60	$1,055.50