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	$220.54	9.734%	$242.0074	$242.01	$242.00	$242.00
Purchase #2	$151.61	13.829%	$172.5761	$172.58	$172.60	$172.60
Purchase #3	$162.83	7.365%	$174.8224	$174.82	$174.80	$174.80
Purchase #4	$59.36	10.835%	$65.7917	$65.79	$65.80	$65.80
Purchase #5	$70.43	4.817%	$73.8226	$73.82	$73.80	$73.80
Purchase #6	$82.61	8.797%	$89.8772	$89.88	$89.90	$89.90
Purchase #7	$208.61	5.339%	$219.7477	$219.75	$219.75	$219.70
7 purchase totals =	$955.99		$1,038.6451	$1,038.65	$1,038.65	$1,038.60