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	$234.46	4.651%	$245.3647	$245.36	$245.35	$245.40
Purchase #2	$234.83	10.686%	$259.9239	$259.92	$259.90	$259.90
Purchase #3	$85.39	5.296%	$89.9123	$89.91	$89.90	$89.90
Purchase #4	$178.51	6.800%	$190.6487	$190.65	$190.65	$190.60
Purchase #5	$41.69	4.578%	$43.5986	$43.60	$43.60	$43.60
Purchase #6	$36.31	5.839%	$38.4301	$38.43	$38.45	$38.40
Purchase #7	$217.68	4.713%	$227.9393	$227.94	$227.95	$227.90
7 purchase totals =	$1,028.87		$1,095.8176	$1,095.81	$1,095.80	$1,095.70