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	$218.32	8.484%	$236.8423	$236.84	$236.85	$236.80
Purchase #2	$93.26	8.217%	$100.9232	$100.92	$100.90	$100.90
Purchase #3	$144.27	7.874%	$155.6298	$155.63	$155.65	$155.60
Purchase #4	$172.55	4.815%	$180.8583	$180.86	$180.85	$180.90
Purchase #5	$21.38	11.812%	$23.9054	$23.91	$23.90	$23.90
Purchase #6	$183.98	3.762%	$190.9013	$190.90	$190.90	$190.90
Purchase #7	$168.57	7.816%	$181.7454	$181.75	$181.75	$181.70
7 purchase totals =	$1,002.33		$1,070.8057	$1,070.81	$1,070.80	$1,070.70