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	$212.80	4.726%	$222.8569	$222.86	$222.85	$222.90
Purchase #2	$37.59	3.456%	$38.8891	$38.89	$38.90	$38.90
Purchase #3	$76.37	6.294%	$81.1767	$81.18	$81.20	$81.20
Purchase #4	$125.28	12.789%	$141.3021	$141.30	$141.30	$141.30
Purchase #5	$230.43	3.321%	$238.0826	$238.08	$238.10	$238.10
Purchase #6	$120.72	4.691%	$126.383	$126.38	$126.40	$126.40
Purchase #7	$38.64	8.288%	$41.8425	$41.84	$41.85	$41.80
7 purchase totals =	$841.83		$890.5329	$890.53	$890.60	$890.60