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	$168.93	12.689%	$190.3655	$190.37	$190.35	$190.40
Purchase #2	$64.60	12.688%	$72.7964	$72.80	$72.80	$72.80
Purchase #3	$173.82	7.423%	$186.7227	$186.72	$186.70	$186.70
Purchase #4	$85.83	7.184%	$91.996	$92.00	$92.00	$92.00
Purchase #5	$232.79	4.214%	$242.5998	$242.60	$242.60	$242.60
Purchase #6	$165.66	4.740%	$173.5123	$173.51	$173.50	$173.50
Purchase #7	$141.33	11.705%	$157.8727	$157.87	$157.85	$157.90
7 purchase totals =	$1,032.96		$1,115.8654	$1,115.87	$1,115.80	$1,115.90