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	$227.39	6.458%	$242.0748	$242.07	$242.05	$242.10
Purchase #2	$61.96	12.493%	$69.7007	$69.70	$69.70	$69.70
Purchase #3	$171.81	8.159%	$185.828	$185.83	$185.85	$185.80
Purchase #4	$179.80	6.587%	$191.6434	$191.64	$191.65	$191.60
Purchase #5	$144.53	5.670%	$152.7249	$152.72	$152.70	$152.70
Purchase #6	$52.56	8.256%	$56.8994	$56.90	$56.90	$56.90
Purchase #7	$188.54	3.466%	$195.0748	$195.07	$195.05	$195.10
7 purchase totals =	$1,026.59		$1,093.9460	$1,093.93	$1,093.90	$1,093.90