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	$113.72	11.464%	$126.7569	$126.76	$126.75	$126.80
Purchase #2	$230.48	8.280%	$249.5637	$249.56	$249.55	$249.60
Purchase #3	$174.30	6.621%	$185.8404	$185.84	$185.85	$185.80
Purchase #4	$104.34	6.429%	$111.048	$111.05	$111.05	$111.00
Purchase #5	$108.82	13.588%	$123.6065	$123.61	$123.60	$123.60
Purchase #6	$220.41	6.193%	$234.06	$234.06	$234.05	$234.10
Purchase #7	$135.52	9.133%	$147.897	$147.90	$147.90	$147.90
7 purchase totals =	$1,087.59		$1,178.7725	$1,178.78	$1,178.75	$1,178.80