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	$167.35	12.542%	$188.339	$188.34	$188.35	$188.30
Purchase #2	$36.50	11.802%	$40.8077	$40.81	$40.80	$40.80
Purchase #3	$250.62	13.825%	$285.2682	$285.27	$285.25	$285.30
Purchase #4	$64.62	9.870%	$70.998	$71.00	$71.00	$71.00
Purchase #5	$157.34	4.526%	$164.4612	$164.46	$164.45	$164.50
Purchase #6	$159.45	3.156%	$164.4822	$164.48	$164.50	$164.50
Purchase #7	$24.70	11.668%	$27.582	$27.58	$27.60	$27.60
7 purchase totals =	$860.58		$941.9383	$941.94	$941.95	$942.00