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	$136.41	6.113%	$144.7487	$144.75	$144.75	$144.70
Purchase #2	$206.76	10.353%	$228.1659	$228.17	$228.15	$228.20
Purchase #3	$200.42	10.523%	$221.5102	$221.51	$221.50	$221.50
Purchase #4	$76.48	6.839%	$81.7105	$81.71	$81.70	$81.70
Purchase #5	$58.71	6.586%	$62.5766	$62.58	$62.60	$62.60
Purchase #6	$106.65	12.812%	$120.314	$120.31	$120.30	$120.30
Purchase #7	$140.94	7.440%	$151.4259	$151.43	$151.45	$151.40
7 purchase totals =	$926.37		$1,010.4518	$1,010.46	$1,010.45	$1,010.40