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	$215.84	9.584%	$236.5261	$236.53	$236.55	$236.50
Purchase #2	$51.78	7.469%	$55.6474	$55.65	$55.65	$55.60
Purchase #3	$38.58	5.717%	$40.7856	$40.79	$40.80	$40.80
Purchase #4	$59.36	10.236%	$65.4361	$65.44	$65.45	$65.40
Purchase #5	$74.89	10.170%	$82.5063	$82.51	$82.50	$82.50
Purchase #6	$50.43	12.333%	$56.6495	$56.65	$56.65	$56.60
Purchase #7	$191.47	10.468%	$211.5131	$211.51	$211.50	$211.50
7 purchase totals =	$682.35		$749.0641	$749.08	$749.10	$748.90