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	$200.52	10.827%	$222.2303	$222.23	$222.25	$222.20
Purchase #2	$103.65	12.645%	$116.7565	$116.76	$116.75	$116.80
Purchase #3	$119.91	6.108%	$127.2341	$127.23	$127.25	$127.20
Purchase #4	$161.96	7.847%	$174.669	$174.67	$174.65	$174.70
Purchase #5	$28.34	10.438%	$31.2981	$31.30	$31.30	$31.30
Purchase #6	$173.34	6.769%	$185.0734	$185.07	$185.05	$185.10
Purchase #7	$203.45	8.115%	$219.96	$219.96	$219.95	$220.00
7 purchase totals =	$991.17		$1,077.2214	$1,077.22	$1,077.20	$1,077.30