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	$139.93	3.771%	$145.2068	$145.21	$145.20	$145.20
Purchase #2	$169.94	12.168%	$190.6183	$190.62	$190.60	$190.60
Purchase #3	$163.60	6.713%	$174.5825	$174.58	$174.60	$174.60
Purchase #4	$144.83	13.591%	$164.5138	$164.51	$164.50	$164.50
Purchase #5	$128.45	8.670%	$139.5866	$139.59	$139.60	$139.60
Purchase #6	$169.89	7.297%	$182.2869	$182.29	$182.30	$182.30
Purchase #7	$226.81	10.552%	$250.743	$250.74	$250.75	$250.70
7 purchase totals =	$1,143.45		$1,247.5379	$1,247.54	$1,247.55	$1,247.50