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	$55.77	6.592%	$59.4464	$59.45	$59.45	$59.40
Purchase #2	$173.37	9.333%	$189.5506	$189.55	$189.55	$189.60
Purchase #3	$191.48	11.642%	$213.7721	$213.77	$213.75	$213.80
Purchase #4	$88.66	8.505%	$96.2005	$96.20	$96.20	$96.20
Purchase #5	$157.66	6.356%	$167.6809	$167.68	$167.70	$167.70
Purchase #6	$147.28	7.462%	$158.27	$158.27	$158.25	$158.30
Purchase #7	$214.59	11.240%	$238.7099	$238.71	$238.70	$238.70
7 purchase totals =	$1,028.81		$1,123.6304	$1,123.63	$1,123.60	$1,123.70