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	$196.64	7.291%	$210.977	$210.98	$211.00	$211.00
Purchase #2	$80.82	6.763%	$86.2859	$86.29	$86.30	$86.30
Purchase #3	$179.37	13.674%	$203.8971	$203.90	$203.90	$203.90
Purchase #4	$203.34	12.565%	$228.8897	$228.89	$228.90	$228.90
Purchase #5	$55.56	10.413%	$61.3455	$61.35	$61.35	$61.30
Purchase #6	$38.94	4.631%	$40.7433	$40.74	$40.75	$40.70
Purchase #7	$250.37	4.346%	$261.2511	$261.25	$261.25	$261.30
7 purchase totals =	$1,005.04		$1,093.3896	$1,093.40	$1,093.45	$1,093.40