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	$88.83	10.597%	$98.2433	$98.24	$98.25	$98.20
Purchase #2	$245.70	3.219%	$253.6091	$253.61	$253.60	$253.60
Purchase #3	$205.47	11.244%	$228.573	$228.57	$228.55	$228.60
Purchase #4	$168.53	3.619%	$174.6291	$174.63	$174.65	$174.60
Purchase #5	$140.61	8.664%	$152.7925	$152.79	$152.80	$152.80
Purchase #6	$161.31	3.533%	$167.0091	$167.01	$167.00	$167.00
Purchase #7	$156.98	6.846%	$167.7269	$167.73	$167.75	$167.70
7 purchase totals =	$1,167.43		$1,242.5830	$1,242.58	$1,242.60	$1,242.50