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	$141.88	11.362%	$158.0004	$158.00	$158.00	$158.00
Purchase #2	$77.95	5.656%	$82.3589	$82.36	$82.35	$82.40
Purchase #3	$158.89	4.644%	$166.2689	$166.27	$166.25	$166.30
Purchase #4	$219.32	13.674%	$249.3098	$249.31	$249.30	$249.30
Purchase #5	$104.82	6.425%	$111.5547	$111.55	$111.55	$111.60
Purchase #6	$145.60	8.579%	$158.091	$158.09	$158.10	$158.10
Purchase #7	$75.53	3.316%	$78.0346	$78.03	$78.05	$78.00
7 purchase totals =	$923.99		$1,003.6183	$1,003.61	$1,003.60	$1,003.70