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	$213.84	7.643%	$230.1838	$230.18	$230.20	$230.20
Purchase #2	$52.61	4.559%	$55.0085	$55.01	$55.00	$55.00
Purchase #3	$133.37	4.299%	$139.1036	$139.10	$139.10	$139.10
Purchase #4	$238.33	5.249%	$250.8399	$250.84	$250.85	$250.80
Purchase #5	$38.76	3.541%	$40.1325	$40.13	$40.15	$40.10
Purchase #6	$167.89	10.399%	$185.3489	$185.35	$185.35	$185.30
Purchase #7	$82.89	4.421%	$86.5546	$86.55	$86.55	$86.60
7 purchase totals =	$927.69		$987.1718	$987.16	$987.20	$987.10