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	$201.54	13.699%	$229.149	$229.15	$229.15	$229.10
Purchase #2	$227.98	9.386%	$249.3782	$249.38	$249.40	$249.40
Purchase #3	$191.85	11.670%	$214.2389	$214.24	$214.25	$214.20
Purchase #4	$65.57	3.235%	$67.6912	$67.69	$67.70	$67.70
Purchase #5	$6.74	12.830%	$7.6047	$7.60	$7.60	$7.60
Purchase #6	$186.83	8.410%	$202.5424	$202.54	$202.55	$202.50
Purchase #7	$83.73	8.381%	$90.7474	$90.75	$90.75	$90.70
7 purchase totals =	$964.24		$1,061.3518	$1,061.35	$1,061.40	$1,061.20