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	$45.73	3.114%	$47.154	$47.15	$47.15	$47.20
Purchase #2	$77.87	3.678%	$80.7341	$80.73	$80.75	$80.70
Purchase #3	$166.34	11.481%	$185.4375	$185.44	$185.45	$185.40
Purchase #4	$50.70	5.716%	$53.598	$53.60	$53.60	$53.60
Purchase #5	$103.46	12.142%	$116.0221	$116.02	$116.00	$116.00
Purchase #6	$171.40	11.597%	$191.2773	$191.28	$191.30	$191.30
Purchase #7	$144.36	4.312%	$150.5848	$150.58	$150.60	$150.60
7 purchase totals =	$759.86		$824.8078	$824.80	$824.85	$824.80