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	$130.88	8.706%	$142.2744	$142.27	$142.25	$142.30
Purchase #2	$217.40	4.106%	$226.3264	$226.33	$226.35	$226.30
Purchase #3	$212.63	10.149%	$234.2098	$234.21	$234.20	$234.20
Purchase #4	$175.74	11.796%	$196.4703	$196.47	$196.45	$196.50
Purchase #5	$88.53	12.419%	$99.5245	$99.52	$99.50	$99.50
Purchase #6	$157.46	3.203%	$162.5034	$162.50	$162.50	$162.50
Purchase #7	$215.77	9.587%	$236.4559	$236.46	$236.45	$236.50
7 purchase totals =	$1,198.41		$1,297.7647	$1,297.76	$1,297.70	$1,297.80