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	$51.32	8.552%	$55.7089	$55.71	$55.70	$55.70
Purchase #2	$99.25	4.384%	$103.6011	$103.60	$103.60	$103.60
Purchase #3	$54.94	11.645%	$61.3378	$61.34	$61.35	$61.30
Purchase #4	$249.71	5.265%	$262.8572	$262.86	$262.85	$262.90
Purchase #5	$127.43	7.709%	$137.2536	$137.25	$137.25	$137.30
Purchase #6	$161.35	11.406%	$179.7536	$179.75	$179.75	$179.80
Purchase #7	$206.29	7.644%	$222.0588	$222.06	$222.05	$222.10
7 purchase totals =	$950.29		$1,022.5710	$1,022.57	$1,022.55	$1,022.70