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	$93.87	3.369%	$97.0325	$97.03	$97.05	$97.00
Purchase #2	$108.94	3.786%	$113.0645	$113.06	$113.05	$113.10
Purchase #3	$70.75	10.340%	$78.0656	$78.07	$78.05	$78.10
Purchase #4	$83.72	6.337%	$89.0253	$89.03	$89.05	$89.00
Purchase #5	$96.33	4.226%	$100.4009	$100.40	$100.40	$100.40
Purchase #6	$151.93	8.109%	$164.25	$164.25	$164.25	$164.30
Purchase #7	$237.58	7.624%	$255.6931	$255.69	$255.70	$255.70
7 purchase totals =	$843.12		$897.5319	$897.53	$897.55	$897.60