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	$80.65	7.849%	$86.9802	$86.98	$87.00	$87.00
Purchase #2	$100.85	11.286%	$112.2319	$112.23	$112.25	$112.20
Purchase #3	$84.61	6.393%	$90.0191	$90.02	$90.00	$90.00
Purchase #4	$176.50	3.578%	$182.8152	$182.82	$182.80	$182.80
Purchase #5	$6.94	5.484%	$7.3206	$7.32	$7.30	$7.30
Purchase #6	$50.68	6.255%	$53.85	$53.85	$53.85	$53.90
Purchase #7	$231.79	11.555%	$258.5733	$258.57	$258.55	$258.60
7 purchase totals =	$732.02		$791.7903	$791.79	$791.75	$791.80