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	$103.46	5.576%	$109.2289	$109.23	$109.25	$109.20
Purchase #2	$19.45	10.142%	$21.4226	$21.42	$21.40	$21.40
Purchase #3	$163.96	3.484%	$169.6724	$169.67	$169.65	$169.70
Purchase #4	$47.37	12.165%	$53.1326	$53.13	$53.15	$53.10
Purchase #5	$244.41	10.511%	$270.0999	$270.10	$270.10	$270.10
Purchase #6	$155.93	10.804%	$172.7767	$172.78	$172.80	$172.80
Purchase #7	$242.31	9.187%	$264.571	$264.57	$264.55	$264.60
7 purchase totals =	$976.89		$1,060.9041	$1,060.90	$1,060.90	$1,060.90