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	$183.75	10.308%	$202.691	$202.69	$202.70	$202.70
Purchase #2	$206.51	6.751%	$220.4515	$220.45	$220.45	$220.50
Purchase #3	$90.99	9.372%	$99.5176	$99.52	$99.50	$99.50
Purchase #4	$172.88	13.860%	$196.8412	$196.84	$196.85	$196.80
Purchase #5	$41.60	10.234%	$45.8573	$45.86	$45.85	$45.90
Purchase #6	$73.66	5.789%	$77.9242	$77.92	$77.90	$77.90
Purchase #7	$101.66	10.716%	$112.5539	$112.55	$112.55	$112.60
7 purchase totals =	$871.05		$955.8367	$955.83	$955.80	$955.90