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	$94.33	11.424%	$105.1063	$105.11	$105.10	$105.10
Purchase #2	$161.30	11.134%	$179.2591	$179.26	$179.25	$179.30
Purchase #3	$16.41	13.285%	$18.5901	$18.59	$18.60	$18.60
Purchase #4	$217.97	7.564%	$234.4573	$234.46	$234.45	$234.50
Purchase #5	$128.67	3.142%	$132.7128	$132.71	$132.70	$132.70
Purchase #6	$114.36	7.153%	$122.5402	$122.54	$122.55	$122.50
Purchase #7	$204.32	8.816%	$222.3329	$222.33	$222.35	$222.30
7 purchase totals =	$937.36		$1,014.9987	$1,015.00	$1,015.00	$1,015.00