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	$42.25	12.757%	$47.6398	$47.64	$47.65	$47.60
Purchase #2	$144.34	5.344%	$152.0535	$152.05	$152.05	$152.10
Purchase #3	$227.99	7.730%	$245.6136	$245.61	$245.60	$245.60
Purchase #4	$89.97	5.406%	$94.8338	$94.83	$94.85	$94.80
Purchase #5	$180.73	11.552%	$201.6079	$201.61	$201.60	$201.60
Purchase #6	$231.34	8.450%	$250.8882	$250.89	$250.90	$250.90
Purchase #7	$140.53	12.768%	$158.4729	$158.47	$158.45	$158.50
7 purchase totals =	$1,057.15		$1,151.1097	$1,151.10	$1,151.10	$1,151.10