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	$196.45	5.610%	$207.4708	$207.47	$207.45	$207.50
Purchase #2	$50.66	11.587%	$56.53	$56.53	$56.55	$56.50
Purchase #3	$18.61	7.811%	$20.0636	$20.06	$20.05	$20.10
Purchase #4	$138.58	9.586%	$151.8643	$151.86	$151.85	$151.90
Purchase #5	$31.45	3.779%	$32.6385	$32.64	$32.65	$32.60
Purchase #6	$136.96	3.846%	$142.2275	$142.23	$142.25	$142.20
Purchase #7	$147.66	11.585%	$164.7664	$164.77	$164.75	$164.80
7 purchase totals =	$720.37		$775.5611	$775.56	$775.55	$775.60