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	$80.94	6.431%	$86.1453	$86.15	$86.15	$86.10
Purchase #2	$20.69	5.666%	$21.8623	$21.86	$21.85	$21.90
Purchase #3	$17.49	3.471%	$18.0971	$18.10	$18.10	$18.10
Purchase #4	$196.84	10.195%	$216.9078	$216.91	$216.90	$216.90
Purchase #5	$49.78	8.518%	$54.0203	$54.02	$54.00	$54.00
Purchase #6	$189.90	10.281%	$209.4236	$209.42	$209.40	$209.40
Purchase #7	$208.40	10.324%	$229.9152	$229.92	$229.90	$229.90
7 purchase totals =	$764.04		$836.3716	$836.38	$836.30	$836.30