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	$150.55	11.761%	$168.2562	$168.26	$168.25	$168.30
Purchase #2	$200.56	13.333%	$227.3007	$227.30	$227.30	$227.30
Purchase #3	$240.42	8.715%	$261.3726	$261.37	$261.35	$261.40
Purchase #4	$107.73	6.196%	$114.405	$114.41	$114.40	$114.40
Purchase #5	$185.49	3.184%	$191.396	$191.40	$191.40	$191.40
Purchase #6	$92.58	8.326%	$100.2882	$100.29	$100.30	$100.30
Purchase #7	$60.61	11.169%	$67.3795	$67.38	$67.40	$67.40
7 purchase totals =	$1,037.94		$1,130.3982	$1,130.41	$1,130.40	$1,130.50