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	$218.50	8.450%	$236.9633	$236.96	$236.95	$237.00
Purchase #2	$134.33	12.867%	$151.6142	$151.61	$151.60	$151.60
Purchase #3	$206.38	9.750%	$226.5021	$226.50	$226.50	$226.50
Purchase #4	$75.28	4.550%	$78.7052	$78.71	$78.70	$78.70
Purchase #5	$145.37	4.709%	$152.2155	$152.22	$152.20	$152.20
Purchase #6	$131.57	4.172%	$137.0591	$137.06	$137.05	$137.10
Purchase #7	$196.73	4.466%	$205.516	$205.52	$205.50	$205.50
7 purchase totals =	$1,108.16		$1,188.5754	$1,188.58	$1,188.50	$1,188.60