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	$108.67	4.533%	$113.596	$113.60	$113.60	$113.60
Purchase #2	$42.62	6.840%	$45.5352	$45.54	$45.55	$45.50
Purchase #3	$54.99	13.419%	$62.3691	$62.37	$62.35	$62.40
Purchase #4	$166.36	3.113%	$171.5388	$171.54	$171.55	$171.50
Purchase #5	$114.69	4.235%	$119.5471	$119.55	$119.55	$119.50
Purchase #6	$60.25	4.285%	$62.8317	$62.83	$62.85	$62.80
Purchase #7	$16.92	6.687%	$18.0514	$18.05	$18.05	$18.10
7 purchase totals =	$564.50		$593.4693	$593.48	$593.50	$593.40