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	$152.77	7.805%	$164.6937	$164.69	$164.70	$164.70
Purchase #2	$20.85	3.212%	$21.5197	$21.52	$21.50	$21.50
Purchase #3	$107.30	6.759%	$114.5524	$114.55	$114.55	$114.60
Purchase #4	$173.65	3.432%	$179.6097	$179.61	$179.60	$179.60
Purchase #5	$59.78	8.154%	$64.6545	$64.65	$64.65	$64.70
Purchase #6	$203.80	6.239%	$216.5151	$216.52	$216.50	$216.50
Purchase #7	$90.50	9.625%	$99.2106	$99.21	$99.20	$99.20
7 purchase totals =	$808.65		$860.7557	$860.75	$860.70	$860.80