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	$47.45	8.407%	$51.4391	$51.44	$51.45	$51.40
Purchase #2	$209.81	8.450%	$227.5389	$227.54	$227.55	$227.50
Purchase #3	$50.45	5.789%	$53.3706	$53.37	$53.35	$53.40
Purchase #4	$102.72	7.641%	$110.5688	$110.57	$110.55	$110.60
Purchase #5	$52.78	12.762%	$59.5158	$59.52	$59.50	$59.50
Purchase #6	$232.97	13.723%	$264.9405	$264.94	$264.95	$264.90
Purchase #7	$93.34	9.136%	$101.8675	$101.87	$101.85	$101.90
7 purchase totals =	$789.52		$869.2412	$869.25	$869.20	$869.20