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	$35.83	3.562%	$37.1063	$37.11	$37.10	$37.10
Purchase #2	$32.38	6.272%	$34.4109	$34.41	$34.40	$34.40
Purchase #3	$37.32	12.609%	$42.0257	$42.03	$42.05	$42.00
Purchase #4	$147.72	6.514%	$157.3425	$157.34	$157.35	$157.30
Purchase #5	$171.35	12.397%	$192.5923	$192.59	$192.60	$192.60
Purchase #6	$145.70	12.837%	$164.4035	$164.40	$164.40	$164.40
Purchase #7	$217.78	6.392%	$231.7005	$231.70	$231.70	$231.70
7 purchase totals =	$788.08		$859.5817	$859.58	$859.60	$859.50