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	$96.64	6.521%	$102.9419	$102.94	$102.95	$102.90
Purchase #2	$153.95	11.449%	$171.5757	$171.58	$171.60	$171.60
Purchase #3	$117.37	9.693%	$128.7467	$128.75	$128.75	$128.70
Purchase #4	$249.39	6.470%	$265.5255	$265.53	$265.55	$265.50
Purchase #5	$119.78	12.347%	$134.5692	$134.57	$134.55	$134.60
Purchase #6	$139.38	9.364%	$152.4315	$152.43	$152.45	$152.40
Purchase #7	$90.37	5.326%	$95.1831	$95.18	$95.20	$95.20
7 purchase totals =	$966.88		$1,050.9736	$1,050.98	$1,051.05	$1,050.90