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	$174.56	13.277%	$197.7363	$197.74	$197.75	$197.70
Purchase #2	$104.71	6.849%	$111.8816	$111.88	$111.90	$111.90
Purchase #3	$182.30	7.778%	$196.4793	$196.48	$196.50	$196.50
Purchase #4	$110.79	3.498%	$114.6654	$114.67	$114.65	$114.70
Purchase #5	$200.82	3.229%	$207.3045	$207.30	$207.30	$207.30
Purchase #6	$204.68	6.183%	$217.3354	$217.34	$217.35	$217.30
Purchase #7	$40.59	11.730%	$45.3512	$45.35	$45.35	$45.40
7 purchase totals =	$1,018.45		$1,090.7537	$1,090.76	$1,090.80	$1,090.80