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	$209.45	11.860%	$234.2908	$234.29	$234.30	$234.30
Purchase #2	$171.97	6.343%	$182.8781	$182.88	$182.90	$182.90
Purchase #3	$196.88	3.594%	$203.9559	$203.96	$203.95	$204.00
Purchase #4	$35.62	12.163%	$39.9525	$39.95	$39.95	$40.00
Purchase #5	$48.70	5.280%	$51.2714	$51.27	$51.25	$51.30
Purchase #6	$106.58	5.843%	$112.8075	$112.81	$112.80	$112.80
Purchase #7	$180.38	6.223%	$191.605	$191.61	$191.60	$191.60
7 purchase totals =	$949.58		$1,016.7612	$1,016.77	$1,016.75	$1,016.90