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	$174.59	4.378%	$182.2336	$182.23	$182.25	$182.20
Purchase #2	$237.69	10.365%	$262.3266	$262.33	$262.35	$262.30
Purchase #3	$84.37	8.244%	$91.3255	$91.33	$91.35	$91.30
Purchase #4	$85.75	9.346%	$93.7642	$93.76	$93.75	$93.80
Purchase #5	$73.63	12.111%	$82.5473	$82.55	$82.55	$82.50
Purchase #6	$166.81	11.403%	$185.8313	$185.83	$185.85	$185.80
Purchase #7	$90.41	10.664%	$100.0513	$100.05	$100.05	$100.10
7 purchase totals =	$913.25		$998.0798	$998.08	$998.15	$998.00