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	$217.96	3.752%	$226.1379	$226.14	$226.15	$226.10
Purchase #2	$176.95	11.144%	$196.6693	$196.67	$196.65	$196.70
Purchase #3	$165.84	12.828%	$187.114	$187.11	$187.10	$187.10
Purchase #4	$176.30	13.129%	$199.4464	$199.45	$199.45	$199.40
Purchase #5	$91.62	13.358%	$103.8586	$103.86	$103.85	$103.90
Purchase #6	$69.54	12.438%	$78.1894	$78.19	$78.20	$78.20
Purchase #7	$165.90	13.179%	$187.764	$187.76	$187.75	$187.80
7 purchase totals =	$1,064.11		$1,179.1796	$1,179.18	$1,179.15	$1,179.20