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	$213.35	11.754%	$238.4272	$238.43	$238.45	$238.40
Purchase #2	$179.61	9.352%	$196.4071	$196.41	$196.40	$196.40
Purchase #3	$228.55	3.851%	$237.3515	$237.35	$237.35	$237.40
Purchase #4	$7.61	10.285%	$8.3927	$8.39	$8.40	$8.40
Purchase #5	$247.31	5.146%	$260.0366	$260.04	$260.05	$260.00
Purchase #6	$137.63	10.119%	$151.5568	$151.56	$151.55	$151.60
Purchase #7	$5.66	7.664%	$6.0938	$6.09	$6.10	$6.10
7 purchase totals =	$1,019.72		$1,098.2657	$1,098.27	$1,098.30	$1,098.30