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	$125.50	7.190%	$134.5235	$134.52	$134.50	$134.50
Purchase #2	$84.77	8.114%	$91.6482	$91.65	$91.65	$91.60
Purchase #3	$171.57	5.518%	$181.0372	$181.04	$181.05	$181.00
Purchase #4	$136.69	4.325%	$142.6018	$142.60	$142.60	$142.60
Purchase #5	$138.43	4.311%	$144.3977	$144.40	$144.40	$144.40
Purchase #6	$151.37	10.499%	$167.2623	$167.26	$167.25	$167.30
Purchase #7	$119.68	3.518%	$123.8903	$123.89	$123.90	$123.90
7 purchase totals =	$928.01		$985.3610	$985.36	$985.35	$985.30