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	$35.86	3.439%	$37.0932	$37.09	$37.10	$37.10
Purchase #2	$112.98	7.154%	$121.0626	$121.06	$121.05	$121.10
Purchase #3	$78.25	9.658%	$85.8074	$85.81	$85.80	$85.80
Purchase #4	$72.77	13.831%	$82.8348	$82.83	$82.85	$82.80
Purchase #5	$68.45	11.870%	$76.575	$76.58	$76.60	$76.60
Purchase #6	$155.31	6.191%	$164.9252	$164.93	$164.95	$164.90
Purchase #7	$185.33	6.735%	$197.812	$197.81	$197.80	$197.80
7 purchase totals =	$708.95		$766.1102	$766.11	$766.15	$766.10