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	$24.72	3.696%	$25.6337	$25.63	$25.65	$25.60
Purchase #2	$101.70	3.127%	$104.8802	$104.88	$104.90	$104.90
Purchase #3	$100.67	4.566%	$105.2666	$105.27	$105.25	$105.30
Purchase #4	$124.58	3.868%	$129.3988	$129.40	$129.40	$129.40
Purchase #5	$67.48	4.109%	$70.2528	$70.25	$70.25	$70.30
Purchase #6	$249.53	11.429%	$278.0488	$278.05	$278.05	$278.00
Purchase #7	$237.41	7.578%	$255.4009	$255.40	$255.40	$255.40
7 purchase totals =	$906.09		$968.8818	$968.88	$968.90	$968.90