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	$55.89	11.119%	$62.1044	$62.10	$62.10	$62.10
Purchase #2	$90.57	3.130%	$93.4048	$93.40	$93.40	$93.40
Purchase #3	$151.83	10.424%	$167.6568	$167.66	$167.65	$167.70
Purchase #4	$168.74	12.150%	$189.2419	$189.24	$189.25	$189.20
Purchase #5	$239.38	9.473%	$262.0565	$262.06	$262.05	$262.10
Purchase #6	$87.65	3.563%	$90.773	$90.77	$90.75	$90.80
Purchase #7	$207.26	11.663%	$231.4327	$231.43	$231.45	$231.40
7 purchase totals =	$1,001.32		$1,096.6701	$1,096.66	$1,096.65	$1,096.70