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	$67.91	6.333%	$72.2107	$72.21	$72.20	$72.20
Purchase #2	$208.71	5.699%	$220.6044	$220.60	$220.60	$220.60
Purchase #3	$89.91	12.410%	$101.0678	$101.07	$101.05	$101.10
Purchase #4	$164.59	10.545%	$181.946	$181.95	$181.95	$181.90
Purchase #5	$143.53	4.250%	$149.63	$149.63	$149.65	$149.60
Purchase #6	$172.96	9.656%	$189.661	$189.66	$189.65	$189.70
Purchase #7	$83.98	6.250%	$89.2288	$89.23	$89.25	$89.20
7 purchase totals =	$931.59		$1,004.3487	$1,004.35	$1,004.35	$1,004.30