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	$198.52	5.814%	$210.062	$210.06	$210.05	$210.10
Purchase #2	$41.57	3.445%	$43.0021	$43.00	$43.00	$43.00
Purchase #3	$144.76	11.838%	$161.8967	$161.90	$161.90	$161.90
Purchase #4	$57.39	10.767%	$63.5692	$63.57	$63.55	$63.60
Purchase #5	$231.83	11.575%	$258.6643	$258.66	$258.65	$258.70
Purchase #6	$82.54	8.422%	$89.4915	$89.49	$89.50	$89.50
Purchase #7	$63.54	11.313%	$70.7283	$70.73	$70.75	$70.70
7 purchase totals =	$820.15		$897.4141	$897.41	$897.40	$897.50