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	$10.94	3.797%	$11.3554	$11.36	$11.35	$11.40
Purchase #2	$53.63	3.838%	$55.6883	$55.69	$55.70	$55.70
Purchase #3	$217.73	6.277%	$231.3969	$231.40	$231.40	$231.40
Purchase #4	$65.52	3.331%	$67.7025	$67.70	$67.70	$67.70
Purchase #5	$125.26	7.177%	$134.2499	$134.25	$134.25	$134.20
Purchase #6	$71.94	8.752%	$78.2362	$78.24	$78.25	$78.20
Purchase #7	$80.82	9.358%	$88.3831	$88.38	$88.40	$88.40
7 purchase totals =	$625.84		$667.0123	$667.02	$667.05	$667.00