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	$233.88	7.161%	$250.6281	$250.63	$250.65	$250.60
Purchase #2	$178.83	8.604%	$194.2165	$194.22	$194.20	$194.20
Purchase #3	$171.86	6.123%	$182.383	$182.38	$182.40	$182.40
Purchase #4	$86.59	3.553%	$89.6665	$89.67	$89.65	$89.70
Purchase #5	$138.46	3.156%	$142.8298	$142.83	$142.85	$142.80
Purchase #6	$126.55	5.676%	$133.733	$133.73	$133.75	$133.70
Purchase #7	$46.47	12.171%	$52.1259	$52.13	$52.15	$52.10
7 purchase totals =	$982.64		$1,045.5828	$1,045.59	$1,045.65	$1,045.50