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	$31.61	13.799%	$35.9719	$35.97	$35.95	$36.00
Purchase #2	$6.52	8.241%	$7.0573	$7.06	$7.05	$7.10
Purchase #3	$55.33	10.453%	$61.1136	$61.11	$61.10	$61.10
Purchase #4	$211.89	6.221%	$225.0717	$225.07	$225.05	$225.10
Purchase #5	$207.43	10.646%	$229.513	$229.51	$229.50	$229.50
Purchase #6	$212.75	4.630%	$222.6003	$222.60	$222.60	$222.60
Purchase #7	$118.27	5.232%	$124.4579	$124.46	$124.45	$124.50
7 purchase totals =	$843.80		$905.7857	$905.78	$905.70	$905.90