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	$134.60	6.145%	$142.8712	$142.87	$142.85	$142.90
Purchase #2	$201.64	3.585%	$208.8688	$208.87	$208.85	$208.90
Purchase #3	$99.29	3.292%	$102.5586	$102.56	$102.55	$102.60
Purchase #4	$46.56	5.419%	$49.0831	$49.08	$49.10	$49.10
Purchase #5	$79.51	3.638%	$82.4026	$82.40	$82.40	$82.40
Purchase #6	$137.34	4.292%	$143.2346	$143.23	$143.25	$143.20
Purchase #7	$179.66	11.538%	$200.3892	$200.39	$200.40	$200.40
7 purchase totals =	$878.60		$929.4081	$929.40	$929.40	$929.50