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	$34.41	10.178%	$37.9122	$37.91	$37.90	$37.90
Purchase #2	$81.47	9.781%	$89.4386	$89.44	$89.45	$89.40
Purchase #3	$117.90	6.543%	$125.6142	$125.61	$125.60	$125.60
Purchase #4	$243.26	5.229%	$255.9801	$255.98	$256.00	$256.00
Purchase #5	$160.25	8.717%	$174.219	$174.22	$174.20	$174.20
Purchase #6	$121.31	12.414%	$136.3694	$136.37	$136.35	$136.40
Purchase #7	$198.64	13.529%	$225.514	$225.51	$225.50	$225.50
7 purchase totals =	$957.24		$1,045.0475	$1,045.04	$1,045.00	$1,045.00