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	$162.85	10.284%	$179.5975	$179.60	$179.60	$179.60
Purchase #2	$237.81	4.446%	$248.383	$248.38	$248.40	$248.40
Purchase #3	$80.76	12.615%	$90.9479	$90.95	$90.95	$90.90
Purchase #4	$166.47	10.336%	$183.6763	$183.68	$183.70	$183.70
Purchase #5	$38.68	6.710%	$41.2754	$41.28	$41.30	$41.30
Purchase #6	$190.80	3.579%	$197.6287	$197.63	$197.65	$197.60
Purchase #7	$63.52	3.731%	$65.8899	$65.89	$65.90	$65.90
7 purchase totals =	$940.89		$1,007.3987	$1,007.41	$1,007.50	$1,007.40