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	$135.54	5.198%	$142.5854	$142.59	$142.60	$142.60
Purchase #2	$148.69	8.243%	$160.9465	$160.95	$160.95	$160.90
Purchase #3	$231.78	4.448%	$242.0896	$242.09	$242.10	$242.10
Purchase #4	$12.95	11.656%	$14.4595	$14.46	$14.45	$14.50
Purchase #5	$59.96	10.645%	$66.3427	$66.34	$66.35	$66.30
Purchase #6	$225.94	9.473%	$247.3433	$247.34	$247.35	$247.30
Purchase #7	$125.46	4.118%	$130.6264	$130.63	$130.65	$130.60
7 purchase totals =	$940.32		$1,004.3934	$1,004.40	$1,004.45	$1,004.30